Trailer Wiring Diagrams (for Non-Electricians)
Trailer Wiring Diagrams
Trailer Wiring Connectors
5-Way Connectors
6-Way Connectors
7-Way Connectors
Mounting Your Trailer Wiring Harness
Trailer Wiring Adapters
Troubleshoot Your Trailer Wiring
Problem: There is no signal going into the box, meaning something is incorrect on the vehicle. Solution: Solve the problem by checking for blown fuses and then check the installation points. Use a circuit tester to check that the correct wires are tapped into, the wiring harness connectors are plugged into the correct vehicle connectors, and check that connectors are plugged in all the way. Problem: If a signal is going in and coming out on the appropriate wires, then there is a problem with the trailer wiring. Solution: Solve the problem by inspecting the wiring on the trailer to make sure all of the connections are correct and ground wires are connected properly. Most likely, the ground wire on the trailer is not secured properly. A trailer wiring system is grounded to the frame near the coupler and each light also needs to be grounded. If there is not a white ground wire coming out of a trailer light, then the light is grounded through its mounting studs. Too much paint, dirt, or rust can cause bad grounds, so make sure the ground is secured to the bare metal frame. Also look for pinched or cut wires; these are often found when wires are routed above suspension components or behind tail lights. Problem: If a signal is going into the box and not coming out or a signal is going into the box and coming out on the wrong wires the ground on the vehicle may not be connected properly. If the white ground wire is not installed properly on the vehicle, then the green and yellow wires will not carry signal coming out of the box. Solution: Solve the problem by checking to make sure the ground wire is installed properly on the vehicle. To make sure you have a suitable ground, first connect the circuit tester's ground wire to the same location as the ground wire on the wiring harness. Then test the signal going into the converter or modulite box. If there is no signal, connect the circuit tester to another grounding location such as the exhaust pipe. If a signal is present, the grounding location for the wiring harness is bad, and a new location needs to be found. On a few vehicles, the frame and body components are not grounded. In these rare instances, look for a ground wire coming out of the license plate light.
Issue: Converter Shorting Out
Too many lights on the trailer. Each incandescent tail light draws about 2 amps and side marker lights typically draw about 0.5 amps each. Most converters allow up to 4 amps to pass through them. A standard converter cannot have any more than 1 tail light on each side. Water. Trailer connectors get wet, causing too many amps to be pulled through the converter. Water can unite all 4 wires on the trailer connector causing it to draw too many amps. This often happens when a boat trailer is backed into water with the trailer wiring still connected to the vehicle. To solve the problem of connections getting wet, always disconnect the trailer connections before backing into the water. Also, covers can help prevent water from getting into trailer connectors when it rains or when a vehicle is taken through the car wash. Bare wires touch each other or the trailer frame. This causes too many amps to be pulled through the converter box. The coating on trailer wires can wear thin, often at the connection to the trailer's tail light or where the wires pass over the trailer suspension. If wires are hung too loosely, they can get pinched and smashed between the trailer frame and suspension U-bolts. To solve the problem, inspect the trailer wires and replace any that are damaged or frayed.
Issue: Weak Ground
The connector on the vehicle should have a ground wire secured tightly to a clean surface on the frame. A wire attached to the body or a surface with undercoating or rust can cause a ground problem. The connector on the trailer should have a wire from the connector secured tightly to a clean surface on the trailer. Each tail lamp assembly at the back of the trailer also must be grounded. This is done in one of two ways. The first is by a separate wire coming from the back of each tail lamp assembly being secured to the frame. The second, and most popular, ground is achieved through the bolts of the tail lamp assembly. In this case, the lamp housing must be attached to the frame of the trailer. If the lights are mounted on wood or PVC material, the light will not receive ground. The last possibility to explore is in the trailer design. If the trailer has a tilting bed, it is possible the ground is not passing through the pivot point, resulting in a poor ground. The solution to this is to route a ground wire from the connector at the front of the trailer to each lamp assembly at the back of the trailer, bypassing this pivot point.
How to Wire your Car or Truck to Pull a Trailer
T-One Connector
Custom Hardwire Kit
Standard 4-Pole Wiring Harness - For use with vehicles that have adequate power and standard wiring system, these simply connect into existing wires on the vehicle and have a 4-pole flat connector to attach a trailer. Converter - For use with vehicles that have separate turn and brake light wires. Some vehicles send only one signal per wire, creating what is called a 3-wire system: one wire for the left turn, one wire for the right turn, and one wire for the brake signal (common on vehicles with amber turn signals). A converter will reduce it to a standard 2-wire system needed for wiring a trailer. There are still additional wires for the running lights and for the ground. Any vehicle with amber turn signals will need a converter. However, there are some vehicles with all-red tail lights that can also require a converter. A wiring harness with a converter has a black box built in it. Five wires go into the box, and only 4 come out. The converter transfers the brake signal on the vehicle into the left and right turn signals for the trailer wiring system. Modulite or Powered Converter - Used with vehicles that do not provide enough electrical power to handle the additional strain of powering trailer lights, the Modulite or powered system draws power directly from the battery but still connects to the vehicle's wiring system to determine when to power the lights on the trailer. If there are too many lights on the trailer for the vehicle's electrical system to provide adequate power, use a modulite or powered converter. A modulite installs the same way as a standard converter except an extra wire must be run to the battery. Instead of drawing power from the vehicle wiring system, a modulite draws power directly from the vehicle battery. This is safer because the extra amps to power the trailer are no longer going through the expensive electrical components of the vehicle. More vehicles are using thinner gauge wire and require a modulite, regardless of how many lights are on the trailer, simply to protect their wiring system.
Larry
9/7/2025
2003 silverado with factory trailer wiring harness. The yellow left turn/ brake wire has no power. All other wires ok. It's not the connector because I bared the wire to test. As far as I know there is no fuse for the one wire. I'm lost as to why it would go dead when nothing in factory wiring has been altered
Robin H.
9/9/2025
@Larry if everything else checks out, and your fuses are fine, it is likely a short in that wire somewhere. You would have to trace it back and repair as necessary.
Larry
9/9/2025
Did actually find a blown left trailer fuse in the panel on drivers side dash. When I looked at panel under hood and googled fuse locations for the truck it didn't indicate such a fuse. Hours wasted for brain fart
Jason S.
8/11/2025
I can't figure out the running lights on my brother's car trailer. When I took the 7 point plug apart there is a white wire with a brown stripe on it that's for the running lights for the trailer. I'm not sure where the wire is supposed to go. Any tips or whatever you have will be helpful.
Jesse M.
8/12/2025
@JasonS The running lights would typically be a green wire going to the 2 o'clock pin on the 7-way. Wire color is not always done to standard though. You can see a typical 7-way diagram here:
www.etrailer.com/question-99177.html
Jason S.
8/12/2025
@JesseM the green wire is the right turn signal wire. There is an empty pin on the plug and I thought that was where the brown wire went
Jim D.
8/8/2025
I am wanting to install and electric tongue jack to my new box trailer with electric brakes and want an independent power source for it. It appears I am using the truck as a ground as I have 5 ground wires attached to the plug ground. I also want my interior lights to run both when it is plugged into the truck and when it is not. So, could I add a chassis ground on the trailer off the battery for the jack, and then add a jumper to the lights so they operate off both the battery and the truck when the light circuit is on? There is a wall switch in the trailer that controls the lights.
Jesse M.
8/8/2025
@JimD Yes you can ground the jack to the battery or to the trailer frame/chassis. You can run a jumper for the lights. Totally fine to wire it that way.
Roel F.
5/18/2025
Good afternoon this question is directed to electrical gurus that like to Tinker. I’m trying to hook up on airhorn to my seven trailer connection. I’ll be using a 12 V always closed solenoid, but my question is if I can act it using my brake controller toggle inside the cab.? Will the horn sound every time I press on my brakes once the 17 trailer connection has been established or will it only be actuate using the brake controller?
Jameson C.
5/20/2025
@RoelF If you were to wire the air horn to the brake output circuit so that it would come on when you slid the override lever of your brake controller it would also activate any time you were towing and you hit the brakes so that's probably not what you were looking for...unless this was a prank you were planning on pulling on someone else's truck.
Roel F.
5/21/2025
@JamesonC I would not have a trailer in tow. Will the truck sense a closed circuit and show that a trailer is plugged in, due to connecting an “accessory” to the 7 pin? Which wire could bypass this? This will activate the trailer brakes with every step of the brake pedal.
This can create many different uses that require low amp and voltage. Maybe a light when tailgaters get to close, just a little flash so they know you are there. How about a compartment door actuator that releases spiked tennis balls? The options are infinite.
Jameson C.
5/21/2025
@RoelF In order for the brake controller to sense a trailer and show a connection there would need to be a load on the circuit that is normally detected by brake magnets. With what you are trying to do I can't guarantee there would be enough of a load on the circuit for there to be a "connection" shown.
We've heard of people wiring in a brake magnet like the part # BP01-225 on the circuit to allow the connection to be made but we've also heard that it doesn't work every single time.
Tom T.
5/16/2025
I purchased a brand new camper and before I left the dealership I checked to make sure all lights and signals were working which they was. I get 200 yards down the road and I see heavy white smoke coming from under the truck. I stop and inspect the issue which was the wiring harness had melted in 3 areas from the back of the plug at the bumper to the oem connector. I've never seen it heard of this.
Jesse M.
5/20/2025
@TomT Dang sorry to hear that happened. Typically when we see smoke and melting wires it is due to a short that is WAY overdrawing the circuits. If I were you I would take that to a shop to have them diagnose and repair.
Fred J.
2/28/2025
I have a Jeep 2020 Wrangler with a modulite for added power but doesn’t seem to have enough power for trailer lights when running lights are on. I have replaced wiring to plug on Jeep as Salt/ water get in connector over winter.4- wire flat . I have a separate battery in the enclosed bike trailer for charging sport vehicles and interior lights. This has dc battery charger I plug in to ac when available. Is it possible to wire this additional battery to my running lights using a relay?
Kate F.
2/28/2025
@FredJ Great question Fred! I am curious on what brand wiring you are using to where you do not have enough power going back to the trailer for the lights? Sounds like you were able to test it, what did it read?
You can use your trailer’s auxiliary battery to power the running lights by adding a relay. This setup makes sure the trailer battery only powers the lights when the Jeep’s running lights are on, so it won’t drain when the Jeep is off. To do this, you’ll need a 12V 40A relay (can find local), a 10-15A fuse ( # SWC9538 and # C58450-1), and some wiring (10-18 AWG, depending on the circuit).
The relay works like a switch. When the Jeep’s running lights turn on, they activate the relay (using 16-18 AWG wire), which then allows power from the trailer battery (10-12 AWG wire) to flow to the trailer lights (10-12 AWG wire). This way, the Jeep’s wiring isn’t overloaded, and the trailer battery only powers the lights when needed.
Please, let me know how it all works out =)
Kenny
1/17/2025
This diagram claims it's for non-electricians. I am an electrician and sometimes the non-electrician diagrams are terrible. This is probably the best trailer wiring diagram I've ever seen! Thanks and keep up the great work!
Jerred H.
1/17/2025
@Kenny
Thanks for the kind words Kenny! You are one of the rare electricians that has had something nice to say, so I really appreciate the positive feedback!
Mary P.
12/30/2024
Hello, I am planning to relocate my batteries from the front tongue of my trailer to the back, since I'm going from wet lead acid to agm. I have a 7 pin and everything is currently connected and working fine with the batteries up front. To move the batteries back, do I just need to get a longer red wire and replace the current one so it reaches the new location? And if I'm moving the batteries back by about 20 feet, do I need to increase the wire gauge? How do I calculate what gauge wire I need? The length would be around 20 feet, and it's connected to two 100Ahr AGM 12v batteries. I want the red wire to charge the batteries while hooked up to the truck and driving (which it does now). But I don't know what the current is, coming from the truck. And do I need a fuse, and if so, what size?
Benjamin
10/24/2024
Super quick here. On my new trailer all new lights my truck has a 5 plug well it’s a 7 but only 4 tabs and the center for backups. Without cutting a bunch of new wires, I have a 5 flat to a round 7 adapter to my truck. The 5 flat has the extra mine is blue wire. The new lights ,(pods) for my backups have just the red and black. I know that the blue wire has to hook to them in what way ? Do I run the red and black wires to the white and brown where does this blue hook? I have lost my self in this and normally I can fix anything, ( Country style ) !!
Kate F.
10/25/2024
@Benjamin Great question. With the trailer wiring there is not a standard on wire colors and functions. The absolute best way to wire a trailer is to follow the function and not the colors. The blue wire on a 5 way is usually the reverse lockout for a surge brake actuator for backing up. Here is a help article where you will find what the 5 way function on the vehicle end: https://www.etrailer.com/faq-wiring-5-way.aspx, from there you will have to match the functions from vehicle to trailer.
John B.
11/25/2024
@KateF
Hi i have a 2017 ford f 450 with a gooseneck trailer, with a 7 prong trailer plug For the trailer and it accidentally got ripped out. I purchased a new 7 plug for the trailer and have everything wired back up. Unfortunately, now I am running into another issue, which is my trailer lights are staying on even when all my other lights are turned off. Any suggestions would be greatly appreciated. Thank you in advance
Kate F.
11/25/2024
@JohnB I would start with the ground, not having a good clean ground can cause all kind of weird issues. Then I would double check the new 7 way and make sure that it is wired up correctly to match the connections on the gooseneck end. Also, when you are having this issue are your headlights on on the truck, and what lights are you referring to, the running lights? You could also use something like a LCD Digital Circuit Tester # PTW2992 to test the vehicle end to see where that power is running through non stop. If you do this troubleshooting and do not find the issue, please let me know. Also, please include the part number of the wiring that you purchased, and please clarify what lights are staying on. If I don't hear from your John, then I will know that you got it all figured out.
Sue
10/24/2024
I have replaced tail lights on a trailer and have what appears to be a ground issue and I’m stuck in my retrofit. When the running lights are on, all lights work on high (braking illumination), when I use the turn signals the appropriate side (L/R) responds but blinks in opposite time from the tow vehicle blinkers. When I step on the brake the lights go out. Can anyone see an obvious issue here? What am I missing? I have a two horse bumper pull trailer that had the pre-LED era 4” round lights as the only rear indicator lights. After nearly getting rear ended with horses in the trailer I am replacing the rounds with 4” LEDs and adding a strip light to each side as well for added visibility. Help appreciated!
Jerred H.
10/24/2024
@Sue
If you can't find a loose ground or a fault in the wiring. I recommend adding the Load Resistor Kit for LED Turn Signals item # DI34ZR. Often times when you swap out old lights for LED's the tow vehicle doesn't always register them correctly and can cause them to do odd things that are similar to grounding issues or not work at all.
Lori
10/15/2024
I would appreciate any guidance. We have a 2023 Riverstone 39RKFB. The back right-side markers are on and we are plugged into shore power. We have cleaned the 7 pin plug (it's dry with no corrosion) and disconnected shore power and battery but nothing works. Can you recommend a solution?
Kevin C.
9/30/2024
@Lou The first step is to check that your power source isn't dead. From there you'll need to trace from the power to the lights to see if there's a loose connection or any damage to the wiring that could prevent power from passing through to the light. What does your setup look like? Do you have a battery directly powering these lights? Are the lights powered by the 7-way cable connection to the tow vehicle? Do you have a battery that's wired to a distribution panel that the lights are wired to?
Lou
9/30/2024
@KevinC okay, i will have to check what is it is dead? The lights are powered by a 7-way cable connection
Kevin C.
9/30/2024
@Lou If you're not getting power from a battery and instead from the 7-way connector then you'll want to test the pins on your tow vehicle's 7-way to ensure that power is coming through and that you don't have a blown fuse. A multimeter # PT89ZR can be used to see if voltage is coming through at the vehicle side connector. If it is and the trailer lights aren't coming on still then I would first check the junction box ground wire on the trailer.
From there you can also plug in the 7-way cable and test at the junction box to see if the signals are coming through. If not then your cable might have a short in it somewhere and would just need to be replaced. If power is coming through you'll just keep moving forward, tracing the wiring for any damage or loose connections until you make it to the lights.
Essentially, you'll just start at the power and work your way back until you either find whatever the issue is or you'll find that the lights are bad if the power is making it to them and know that the lights just need to be replaced. I try to section it out a bit just help narrow down where the issue might lie.
John B.
11/25/2024
@KevinC
Hi i have a 2017 ford f 450 with a gooseneck trailer, with a 7 prong trailer plug For the trailer and it accidentally got ripped out. I purchased, I knew 7 plug for the trailer and have everything wired back up. Unfortunately, now I am running into another issue, which is my trailer lights are staying on even when all my other lights are turned off. Any suggestions would be greatly appreciated. Thank you in advance
Kevin C.
11/25/2024
@JohnB If the lights are staying on then that means power is getting to them somehow. You'll need to recheck your wiring and make sure everything has been spliced back into the correct pins in the new 7-way and that there's no contact between the wires. The 12v power lead that runs to the 7-way is likely touching the wires for the lights somewhere allowing power to pass through to them even though you have them turned off.
Isaac H.
9/26/2024
2012 Sonoma 20 ft Trailer My brakes do not release while trailer is hooked up either by battery or towing vehicle. If I unplug everything including battery breaks release Cannot figure out what my issue is?
Jameson C.
9/26/2024
@IsaacH Do you have a short from the battery to the frame of your trailer possibly? That's normally what causes that.
John B.
11/25/2024
@JamesonC Hi i have a 2017 ford f 450 with a gooseneck trailer, with a 7 prong trailer plug For the trailer and it accidentally got ripped out. I purchased a new 7 plug for the trailer and have everything wired back up. Unfortunately, now I am running into another issue, which is my trailer lights are staying on even when all my other lights are turned off. Any suggestions would be greatly appreciated. Thank you in advance
Jameson C.
11/25/2024
@JohnB So this is a pretty common issue after installing a replacement 7-way. I have been here before as well. What is happening is that your 12 volt accessory circuit is shorting out to most likely your trailer running light circuit. Since the pins are all close together this is easier to do than you'd think. If you go over the wiring look for any exposed wire that is touching and clean up and also make sure you have the wires ran to all of the correct circuits.
Mike S.
9/22/2024
I have a new boat trailer with a 7 pin. I have no brake lights. I had brake lights etc when I first got it 1 month ago. I found many bad slices and worn wires on the trailer. I started with a new 7 Pin retired with new wire from front to back. All other functions work. Both turn lights work. I then figured out the there is no power/signal to the plug on the truck side. Yet there is still turn signal there. They are supposed to be on the same circuit. I replaced the truck receptacle thinking that was the culprit. No luck.. I have checked the 2 fuses under the hood labeled turn/brake. Both 10 amp fuses were fine on the ohm meter. Truck is 1999 Silverado I have had since new. I have not spliced up any of the wires. It all original. I have used this to pull my old boat with a flat 4 connectors for 25 years. Never an issue. I am going to check the back of the new trailer pin receptacle to see if there is power there and then follow the wires up to the main junction box on the frame. I have already pulled each of these wire bundles and checked for bad pins etc and they are all appear perfect. I have seen some pictures on line of this junction area being badly corroded etc. Mine is near mint. Not sure where to go from there. Any advice? I’ve scoured the webs looking for ideas. Thanks
Mike S.
9/22/2024
@MikeS
Well here is an update. After more trouble shooting it seems I have power at the main 7 pin receptacle however it is only 8 volts. Not enough to light the trailer brake lights. I forgot to clarify earlier that the truck brake lights are fine. Just the trailer brake lights done go. I am thinking weak ground somewhere? My kid did install aftermarket LED taillight assemblies so I checked them and they work just fine. I cleaned off all those connections with a file to expose fresh copper. Still no luck? Now what….
Jameson C.
9/23/2024
@MikeS Can you test to see if the LED lights are getting 12 volts? How did he wire them to the vehicle? It could be a bad ground but the LED lights seem like the most likely culprit since if wired in improperly they can cause lower voltage/current.
Jimmy L.
8/27/2024
My inverter is shorting out. A spark comes from inside the box from a reostat the size of a D battery. It's wet to the touch. But I don't think it is water. I have checked short ground on every plug and wire coming in to the breakers. I'm stumped! Thanks
Jameson C.
8/27/2024
@JimmyL Yeah that's a problem for sure. As bad as it sounds I would find an electrician in your area to go over the setup but in meantime I would cut power to the inverter. Might just be easiest to replace it.
Phil M.
8/25/2024
I tow an RV Trailer with my Subaru Ascent using a Subaru-installed 7-pin connector. I also use a brake controller connected to the wiring harness that accesses the 7-pin. After some challenges, our Subaru dealer repaired the 7-pin connection. My RV trailer lacks reverse lights. At this time, turn signals, brake lights and brake controller work great, but there's a lack of running lights. Would that indicate the #3 pin is not wired correctly or would it indicate a grounding problem. Trying to get back on the road for some fall camping!
Kyle S.
8/26/2024
@PhilM It's likely a ground issue; you can use a circuit tester to see if that pin is getting power, but my guess is the running lights don't have a great ground.
Philm
8/26/2024
@KyleS thank you! Would you predict it's the car, connectors or trailer grounds?
Kyle S.
8/26/2024
@Philm My best guess would be grounds on the trailer. It's pretty common for that to be the main issue with running lights; they're annoyingly finicky when it comes to having a bad ground.
Hil M.
8/20/2024
On 7-pin 2020 Orangeline utility trailer, lights won't work (except the license plate lights) when truck (aftermarket 7-pin) has headlights or running lights turned on. NO headlights, all turn signals and brake lights are fine. Horse trailer that truck pulls is fine. This just a brown pin connection thing? How to test there's even power getting to that running light pin on trailer? Thanks.
Bryce D.
8/20/2024
@HilM Sounds like it could be a ground issue honestly. I recommend checking the ground connection and make sure that it is connected to a clean bare metal surface free from rust. If it's not, then I'd suggest re-grounding it and check to see if that fixes it.
Dennis D.
8/12/2024
On my 2012 three horse slant trailer, a mouse chewed the white and black wires that connect to my interior lights. How do I reconnect them so I can get them working again?
Bryce D.
8/13/2024
@DennisD Dennis, you can just use some butt connectors to reconnect those wires back together. For 12-10 AWG you'll want # DW05745-10, for 16-14 AWG you'll want # DW05744-10, and for 22-18 AWG you'll want # 05730-5.
Dennis D.
8/13/2024
@BryceD
I could not see where the black and white wire connects to the power source. There is a red wire running along the inside of the trailer (7 prong plug) which should power the lights inside. I assume the white wire would be the ground.
Bryce D.
8/14/2024
@DennisD Dennis, can you send some pictures to [email protected], I'm having a hard time picturing what you're describing.
John B.
11/25/2024
@BryceD
Hi i have a 2017 ford f 450 with a gooseneck trailer, with a 7 prong trailer plug For the trailer and it accidentally got ripped out. I purchased a new 7 plug for the trailer and have everything wired back up. Unfortunately, now I am running into another issue, which is my trailer lights are staying on even when all my other lights are turned off. Any suggestions would be greatly appreciated. Thank you in advance
Bryce D.
11/25/2024
@JohnB This is fairly common, and most of the time this is caused by a shorted trailer cord or mis-wired trailer plug. Considering you just swapped your 7-way I'd bet that's your issue.
Gordong
8/3/2024
Good article however there is no coverage of how to wire in a trailer brake breakaway switch.
Jaysonb
7/28/2024
Great resource, thank you! Just curious though - I have a 2022 Toyota Tacoma Limited with the factory installed towing package. I just installed a Redarc brake controller following your eTrailer's recommendation and the install video was very helpful. My question is: Is there anything different about Toyota's 7-pin? I just rewired my equipment trailer and want to make sure I'm not missing anything. At first glance the pin-out from the factory receptacle on the truck doesn't look the same as what everyone says is standard, but maybe that's just my tired eyes. Thank you.
Jon G.
7/29/2024
@Jaysonb Happy to help!
The OEM 7-Way on your 2022 Toyota Tacoma will have the standard connector and functions, yes. The only time it should differ is if someone changed it out on their own and chose something that wasn't industry-standard.
Jaysonb
7/29/2024
@JonG Thank you for the reply. In this case I'm the original owner and it was factory installed so no changes on my end. The one strange thing I'm seeing is that the standard Toyota "green" pin for run lights has no power with lights on or off, but black does have power (with ignition on) so that isn't too big of a deal. Still strange though, as everything else seems to be right. Just curious if this is something you might have seen before?
Jon G.
7/29/2024
@Jaysonb Good to know!
The wiring colors that we typically see (listed in the article) can vary from vehicle to vehicle unfortunately. As long as you have the functions in the right place then you'll be good to go!
Matthew
7/22/2024
i have a 5 pin connector for a rv and the blue wire i was told is back up. Ive run that wire to the reverse lights on my rv and when i put it in reverse I get nothing. The reverse light has a red wire and a ground. the other lights have the typical signal brake and marker lights. how do i get the reverse lights to work?
Bryce D.
7/22/2024
@Matthew It sounds like you've wired everything to the right spot. Are you seeing any voltage on that circuit?
Bryce D.
7/22/2024
@MatthewR To use a circuit tester # PTW2993 you'd need to attach the alligator clip on a circuit to the negative terminal on your battery and then use the other end to touch the wire. The light on the circuit tester should illuminate if there is voltage flowing.
John B.
11/25/2024
@BryceD
Hi i have a 2017 ford f 450 with a gooseneck trailer, with a 7 prong trailer plug For the trailer and it accidentally got ripped out. I purchased a new 7 plug for the trailer and have everything wired back up. Unfortunately, now I am running into another issue, which is my trailer lights are staying on even when all my other lights are turned off. Any suggestions would be greatly appreciated. Thank you in advance
Bryce D.
11/25/2024
@JohnB This is a common issue, believe it or not. Most of the time this is caused by a shorted trailer cord or mis-wired trailer plug. Considering you just swapped out your 7-way, I'd be that's your issue.
Terry
7/1/2024
My rv lifepo4 (14.6v) batteries are back feeding to my truck and causing the trailer brake to error and not work; can't I just remove the positive connection in the system? isn't the 12V on the 7 pin just AUX and not used other than to power the breakaway box; can I / how can I remove the 12v connection that is backfeeding to the truck, I don't need that right?
Paul
7/13/2024
@Terry Place a diode in line on the trailer side just after the plug. make sure you orientate the diode correctly so not to backfeed. This will not allow any 12+VDC to back feed the truck.
Martin
6/21/2024
I would like to say this is the most complete source of info I have ever seen Thanks
Kenneth
5/14/2024
The "E-Trailer" branded graphic called "7 Way RV Plug Wiring" is at odds with everything else on this page, and seemingly with other sources. I'm just looking to begin diagnosing a brake problem on my own trailer...
Moe
5/14/2024
My signal works good left side try right side all lights blinking even clearance lights
Joseph
4/21/2024
I have a 2001 GMC Sierra 3500HD with no factory installed trailer connection. How do I connect the red controller wire to the brake switch or other brake light cold wire? Thanks,
Jon G.
5/15/2024
@Joseph You'll just need the Custom Wiring Adapter # C51342 which plugs in on a port under your driver's side dash and then you either plug into a Curt controller or cut off the black connector and hardwire to the pigtail at the back of your brake controller. You will match the wires color for color for this.
If you check out the product page you'll see where this port is located on your 2001 GMC Sierra 3500HD.
I'm also attaching a link to a helpful article about installing a brake controller on older GM vehicles for your reference.
Helpful Links
Jan M.
1/9/2024
I rewired my boat trailer per instructions, but no lights. Troubleshooting included rechecked ground (white) wire, used a volt meter to check the car 4-way connector, each light wire and even the bulb socket. All had power. Still no lights when I put the bulb in the socket. Any ideas? Thanks
Mike L.
1/9/2024
@JanM How did you do the main ground coming off the trailer connector? We recommend sanding down a dime sized area around the ground connection, and using a star washer between the ground ring terminal and the trailer frame. This provides a good bite into the trailer frame which ensures you'll have a bullet proof ground connection. How are the lamps grounded? You need to make sure those connections are secure as well. If the lamps ground via the mounting studs, be sure the studs attach to clean, bare metal. If they use a separate ground wire, use the method we mentioned above using a star washer. Hope that helps!
Jan M.
1/9/2024
We checked the power along the wiring along each side of the trailer. There was power at each light fixture (4) and we even took off the light cover and checked the bulb socket on the rear lights. The sockets had power, but when we put the bulbs back in, no light in the bulb.
The instructions vaguely mentioned the market lights needing a white ground wire. The market light fixtures did not have a white wire to ground. Nor do the tail lights.
We will modify (add a star washer) our ground wire that is attached to the connector and trailer (as you suggested). On the original setup for this old trailer, the connector ground wire ring was attached to the trailer along with the safety chain. So, that’s how we assembled the new one. Should we just attach the ground ring by itself to the trailer? Thanks
Mike L.
1/10/2024
@JanM If the lamps don't have a separate ground wire, they'll pick up their ground connection by being bolted to the trailer frame. If the aren't bolted directly to the trailer frame, you'll need to make a jumper wire (a short wire with a ring terminal on each end) to connect the lamp's mounting stud to the trailer frame. As far as the main ground, is the metal it's connected to clean and free of corrosion and dirt? Is there a thick layer of galvanized coating on it? The ground connection needs to be in direct contact with the metal of the trailer frame.
Phloridaphil
1/24/2024
@MikeL
Mike
Maybe a good, affordable product for etrailer to stock for sell is a bonding brush. They are a 1/4 shank with a round stainless, crimped wire brush that have different size pilots, #10 pilot for most applications. I use one and my lights are always reliable. I can send you a picture of one.
Mike L.
1/24/2024
@Phloridaphil That's a good idea. I'll get with our product acquisition folks to see if we can make that happen.
Jan
1/24/2024
@MikeL we finally figured it out. The trailer is a tip trailer. We did repaint the trailer, and the ground wasn’t making contact through the tip area to the lights. Thanks for your help.
Mike L.
1/24/2024
@Jan We're glad you found the issue! Ground problems will make trailer lights do all sorts of crazy things...
Chad
12/9/2023
Hello, I have a 1999 GMC digger Derrick utility truck and it has a round 6 pin plug on the truck side. The trailer I'm going to pull is a large 37' pole trailer and the trailer has a 7 pin round plug. I can't find an adapter anywhere and I think I have to build my own, need some help!
Chad
12/11/2023
@MikeL no, that connector is a spade and my trailer is a commercial style plug with 7 round pins. That needs to get wire to the truck side which has 6 round pins
Neil W.
11/12/2023
Awesome page. I’m trying to replace my 6-pin plug with a 7-pin on my gooseneck trailer. Brakes have worked great with an adapter in the past. When I look at the wiring in the 6-pin, the brake pin is not connected and there isn’t a blue wire. Just a black wire on the 12V center pin. I noticed the page said “Note: In some applications, the black battery power connection and the blue brake controller output connection are reversed.” I’m totally confused how the brakes have been working with the factory brake controller without the brake pin being used. Any help would be appreciated.
Jenny N.
11/17/2023
@NeilW What I recommend is to use a circuit tester, like part # PTW2993, behind the trailer connector and test the functions of the wires. Trailer wiring does not always use standard colors and the wiring for the brakes may be black on yours. This should clear up the mystery and allow you to wire the seven way connector in its place.
Neil W.
11/17/2023
@JennyN Thanks! I later found out that the wiring in the old plug was not standard. However, the previous owner "corrected it" inside the adapter. I was able to wire up the new plug and it works great.
Daulton R.
11/8/2023
Thank you for providing the guidance and instruction that you do. It is extremely helpful for a lot of people. The more I visit your site the more I want to come back for help, and purchase from you.
Jenny N.
11/16/2023
@DaultonR Hey thank you for the kind words! Feel free to post a comment or ask a question at any time. We appreciate ya!
Daulton
11/17/2023
Come to think of it I do have a question related to a trailer modification. I tore down an old nasty Shasta trailer and I am making some modifications to the frame. I haven't done a title search but I do have a bill of sale. Should I have taken the trailer to the DMV before I did any changes to the frame? It still has the original numbers stamped on the tongue. I am adding a foot of length. Do I have to have the trailer bed finished or can I take it in with just the frame. I have finders and will add lights, etc next. Thank you for your comments and your time.
Jenny N.
11/17/2023
@Daulton Sounds like a challenge and I would love to be able to answer that for you however each state has their own rules when it comes to trailer regulations. I know it may not be the most fun of experiences however reaching out to your local DMV is going to be the best bet to answer this question,
Daulton
11/18/2023
@JennyN Thank you Jenny. The DMV isn't far from here as well as my 3A insurance office. I'll try the insurance first then make my appointment for the title search and inspection. Lots to do. I'll probably have to have it weighted as well.
Ian
4/25/2024
@Daulton for a homemade trailer with yours will be at that point it does not require it to be tagged or inspected
Pj
10/26/2023
We bought a brand new 2023 dump trailer at auction. It was made in Mexico and does not have standard color-coded wiring. We have all lights and brakes, but when we turn on the headlights of the tow vehicle, the brakes on the trailer come on and stay on.
Mike L.
11/12/2023
@Pj The connector on your trailer is wired incorrectly. You'll want to wire it by function, not by wire color. You'll want to apply 12V to each wire on the trailer's connector to see which function each circuit carries then wire it correctly according to the chart in the linked article.
Helpful Links
Char
10/21/2023
I have a 2008 Dodge Ram 1500, with an unplugged blue plug labelled "Electric Brake" under the dash, but only a 4-flat connector at the rear. What do I need in order to utilize the electric brakes on my trailer?
Nik C.
10/24/2023
@Char you need a trailer brake controller. I use and reccomend a Tekonsha Prodigy P3 controller, available here at etrailer.
Mike L.
11/9/2023
@Char Nic C. is correct. Install your brake controller of choice, use the correct brake controller harness like # 3020-P for a Tekonsha brake controller. You'll need to sever the blue wire exiting the rear of the controller, and attach it to the blue wire you found under the dash. At that point, you should be good to go. Let us know if you have any questions!
Char
5/8/2024
@MikeL
Thanks. I bought a Tekonsha Prodigy P2 controller. Questions... 1) Would the white plug on your 3020-P harness plug into the vacant big blue 4-terminal socket (with wires labeled "Electric Brake") that is under the dash? Why is this blue socket even there since there's no 7-round connector at the rear of the truck? 2) I have a 4-flat connector at the rear but I'll need a 7-round connector and I can find no existing wires in the rear (other than those feeding the truck lights and 4-flat connector) to feed a 7-round connector, so how would I get from the blue socket wiring, with 3020-P plugged in to the blue socket, to the rear?
Mike L.
5/15/2024
@Char The blue connector you described that's located behind the e-brake pedal is the correct place to plug in the # 3020-P harness.
If the truck didn't come with the factory 7-way, Dodge didn't run the wiring to the rear of the vehicle for the brake controller. To finish the installation, you can use our # ETBC7 install kit. The kit includes the 7-way adapter that will plug into your existing 4-flat connector along with the wire that runs to the front of the vehicle. It so happens that we have a video that shows the exact procedure you'll need to follow, I'll link that for you. Ignore the section where our installer removes the 4 pole connector.
Mike L.
11/9/2023
@Nick Depending on the year/make/model vehicle, we might have an install video that you might find helpful...
John M.
10/17/2023
I have purchased a used 1992 Bigfoot 17 travel trailer. When connected to my 2009 Dodge Nitro I get RT and LT lights working properly, as are the brake lights and flashing lights.. I do not get running lights working. My buddy connected with his 2015 Cherokee and we got the same result. I have replaced the 7 pin connector - thinking it was faulty - but the same situation exists. My buddy's Cherokee has factory installed trailer brake and when he pulled the trailer the brakes seemed to be working ok. The 12V trailer battery has not been connected through all of this testing. Your thoughts please. Thanks.....john
Mike L.
10/17/2023
@JohnM I'd recommend checking two things. Check the main trailer connector ground which is typically found on the trailer tongue. Make sure the connection is securely made to clean, non corroded metal. Check your taillight assemblies, make sure those ground connections are secure as well. Even though all the other lamp functions work correctly, a poor ground will make all sorts of crazy things happen, so it's worth checking. Since you've tried the trailer on other vehicles, the problem is obviously in the trailer wiring somewhere (good job there!!). If the grounds are in good shape, check the running lamp circuit on the trailer, beginning at the trailer connector. The running lamp circuit is usually carried by the brown wire. Make sure the wire that carries that circuit doesn't have any loose connections, or isn't pinched. Look for worn or cracked insulation on the wire that might cause a short circuit. Those are the usual suspects to check out...
Charles
10/10/2023
Hello, I just got a vintage 1988 mallard 28rks 5th wheel. When I got it all d.c. and 12 volt items worked. May have been on shore power I'm not sure. Anyway after trying to hook up the battery nothing worked not even a light. Checked converter all connections look correct. Followed out. Negative is a copper wire coming of Negative of panel going to bus then down into floor to frame. Positive I followed to crossover where it goes into the wall. Another black wire comes out of the wall and goes toward battery. From what I can tell, black Positive wire goes to 6 pin connector which goes to a box with 3 wires all black not hooked up and the ground wire on the connector is not attached at the screw. 1, is this the issue? 2. Can I connect all 3 wires with no issue. 3. Technically can't I hook all to positive as long as my negative goes to frame as needed. Thanks
Mike L.
10/11/2023
@Charles After reading your description, we're having difficulty following what you've got going on there. It sounds like you've got a complicated issue happening, and your best bet would be to have your local RV shop have a look at it.
Beth
9/18/2023
I want to put a wireless backup camera on my travel trailer, wired into a rear marker light. However, I'm told this camera won't work if I'm pulling the trailer with my 2021 GMC Sierra, because of something called "Pulse wave modulation" causing the camera to not get enough voltage to work? Is there a solution or work-around for this issue?
Beth
9/19/2023
@MikeL Thanks! So, this adapter goes into the 7 pin connector on the back of the tow vehicle, and then the trailer cord is plugged into that instead?
Also, will this work with any back up camera, or only certain brands?
Mike L.
9/19/2023
@Beth Yes, that's correct. We know for sure that it works with Furrion camera systems, but it has worked with every other camera system we've tried. Which system are you using?
Beth
9/20/2023
@MikeL I just started shopping for one, when I came across the comments about the GMC trucks, so thought I'd do more research, since that's what I drive.
Murat
9/10/2023
Hello All. I need help with loosing power on my Prolite Plus S. After 3 months we went to a short trip and on our stop suddenly light went off inside the camper. It was connected to my Model 3 through Curtis bluetooth controller. When I check the car side power with a multimeter there was no power coming to 7pin connector( I learned that model 3 have electronic breakers it reset it self after sometime). Wait for 24 hours and connected the controller back to car and started to work. Then I connected to camper and loose the power again. I think there is short in the camper but I checked the all fuses and breakers they were all good. Please any idea helps…
Mike L.
9/14/2023
@Murat I doubt you have a short in the trailer wiring, otherwise the LED on the Curt # C51180 Echo would indicate a wiring problem (see linked instructions). This sounds like a problem with either the tow settings on the vehicle or a wiring issue on the vehicle. If that's the case, you'd want to check with Tesla about that.
Kennys
8/21/2023
Can anybody tell me if the batt wire lead on a 7-pin can be used to keep a 12v Batt charged that is used to run aerators on my fish hauling trailer? Is there any amp output info available?
Mike L.
8/22/2023
@Kennys The 12V feed from the trailer connector can be used to keep a battery topped off, but it won't charge a dead battery. On most vehicles, that circuit is protected by a 30A fuse.
Phil L.
8/9/2023
Where can I find yellow & brown & green & brown trailer wires together to rewire my utility trailer
Mike L.
8/10/2023
@PhilL It sounds like you currently have a wishbone-type harness on your trailer, with the running lamp circuit split in two so one leg can feed each side of the trailer. If that's the case, we carry replacement harnesses in different lengths. For 18 feet, check out # 002402. For 30 feet in length go with # A20WB or # A40W42B for a 40 foot length. Let me know if that's not what you had in mind.
Craig V.
7/19/2023
Have a 2018 camper which is almost brand new used very little keeps blowing left turn signal fuse. Also have 2001 Hallmark trailer that blows the same fuse hard to believe 2 trailers have shorts on same circuit. Think it could be on the truck side?
Mike L.
8/2/2023
@CraigV Either the trailer connector on the vehicle is corroded/damaged or there's a short in the left turn/brake circuit (usually the yellow wire) feeding the trailer connector. Look for a wire with cracked or missing insulation or a pinched wire. Give that a look-see, and let us know what you find.
Russ
7/17/2023
OK so just bought an older RV and it has a 4 Pole round socket at the hitch, I have use of a small trailer with a 7 blade round plug. Question is is there an adapter available to plug the 7 into the 4 on the RV? The 7 blade was used on trailer to plug into a truck with an existing 7 blade at the hitch but trailer has no brake, back up light or 12v supply.
Russ
8/2/2023
@MikeL thanks for the reply, I’m going to remove the 7wire from the trailer and wire in a flat 4.
I’m going to change the round four on the Winnebago to a 7blade and flat 4 combo, I found extra wires taped off from when someone removed the original Winnebago socket and badly installed the round 4 socket
Russell
6/29/2023
I have a 7 & a 4 pin connector on my 2020 rv my question is I have a hitch mounted storage box that needs lights and a reverse light I was thinking of using the 7 pin for storage box and 4 pin for boat lights, would there be a problem with that? Also what wire on the 7 pin is reverse light? Thanks
Heather A.
7/17/2023
@Russell I believe you are saying that you have a 7 and 4 pin option on the vehicle side like part # HM40950. Both options can be used simultaneously as long as you don't overload the amperage rating or you will blow the fuses. With that being said, if your actuator on the boat trailer has an electric lockout you will need the reverse signal from the 7-way to power that lockout solenoid. The reverse circuit on the 7-way is the center pin. If are referring to the trailer side wiring, I would probably need a photo of your setup to help.
Jose A.
6/25/2023
I have a 7 pin connector but the wires that were ran do not have a blue wire. Just green black brown yellow red. I hooked wires up with out the blue and the back tire on my trailer locks up?
Mike L.
7/15/2023
@JoseA Are you speaking of the wires feeding the 7-way on the tow vehicle, or on the trailer?
Marc
6/5/2023
Hello I have a 2012 Jayco X23b. I am having a problem with the right rear light assembly. Under normal conditions, the brake light and turn signal on the right side work as they should but when you turn on your marker lights for the entire trailer, the right rear light becomes extremely bright, will not show the brake light working or the turn signal. Just stay is extremely bright. Now if you turn the power off to the marker lights, it works like it should turn signal and brake light work together. it is not on the vehicle side I pull a boat trailer and a flatbed trailer as well and do not have that issue with either one of them. Any ideas.???
Mike L.
6/6/2023
@Marc What you describe is a classic system of a poor ground connection. Starting at the trailer connector on the tow vehicle, make sure the ground is securely connected to clean, bare metal. On the trailer, the trailer connector will usually have its main ground on the trailer tongue. Make sure that's secure and not corroded. Same with the right rear taillight. To make a bomb-proof ground connection, sand a dime sized area down to bare metal around the frame/chassis ground. Sandwich a star washer between the ring terminal and the frame/chassis. This will bite into the frame for a strong ground connection. Finally, give the area a quick shot of rust inhibiting spray paint like Rust Oleum to protect it. You'll be good to go then. Let us know how it works out!
Cory
1/13/2024
Sounds like it could be the right turn signal/brake light wire is swapped with the tail/marker lights wire: When the turn signal is on, it is flashing what should be the (dimmer) tail light, and when the marker lights are on it is turning on what should be the (brighter) turn signal/brake light. With the brighter "tail light" on, the dimmer flashing turn signal would not be very noticeable.
Marc
1/14/2024
@Cory that was the problem shortly after contacting etrailer I decided to pull both rear lights out to check the wiring and it was crossed on the passenger side light. Been golden ever since
Michael
4/27/2023
I purchased a Tekonsha T-one Wiring Harness With 4-pole Flat Trailer Connector for my 2017 Range Rover Sport, I tested it and it doesn't seem to receive any electricity. The fuse is ok. I hope someone can give me some advice.
Mike L.
4/27/2023
@Michael I'm assuming you're using # 118681. Make sure the connector is properly grounded to clean, bare metal. If that checks out okay, unplug the T-1 connector and use a circuit tester like # PTW2993 on the vehicle's connector where the # 118681 plugs in as you activate each taillight function. If you're getting signals, the # 118681 harness is faulty and should be replaced. If you aren't getting signals at that connector, there are actually several fuses involved with the tow wiring functions. You'll want to check the following:
In the passenger cabin:
• # 5
• # 27
• # 48
In the cargo compartment:
• # F5
• # F22
Check all those fuses to make sure they're all good. Let us know how it works out.
Helpful Links
Michael
4/27/2023
@MikeL Thank you! I will check all of this out and let you know if I was able to fix it! "brb" ;)
Michael
4/27/2023
@MikeL regardless that none of the fuses were actually bad, I swapped them out for new ones anyways and I am still not get any signal from the vehicle connector plug unfortunately.
Not sure what else it can be.
Mike L.
4/27/2023
@Michael If the fuses are good, and you're not getting any function from the vehicle plug with the Tekonsha harness unplugged, that's a vehicle problem you'd need to get checked out via a mechanic or the dealer. The only other option would be a hardwired harness like # C59496 that would tap directly into the taillight circuits which would bypass any issues in the vehicle's tow package...
Derek
4/17/2023
Brakes not working on 5th wheel, 2012 Montana 3400rl brakes not working, use a 2013 chevy 2500hd truck. I hook up camper cable to truck all the lights work but while doing a brake test nothing no trailer brakes even slideing brake controler form low to highest nothing no change. truck does not even acknowledge trailer brake hookup. I changed truck plug first easy enough no change, could not find any bad wires under camper from brakes, check ground wires nothing I did just get new tires put on not sure if that could have done it, before I start spending more money for no change, I could use some advise on this problem..please.
Marcus
2/12/2023
I have a Tekonsha Primus IQ and the wires in my 2022 Tahoe are run but not in a connector. There is a wire labeled “to trailer” does this go to the input or output of the wiring harness?
Mike L.
2/15/2023
We got you! The blue wire you found carries the output from the controller to the trailer connector then to the trailer brakes. Along with that blue wire, the tow package harness under the dash should also include a red/black striped, a white, a light blue/white striped and and orange wire. These wires connect to the pigtail included with your brake controller as follows:
• Red/black tow package wire to black pigtail wire
• White tow package wire to white pigtail wire
• Light blue/white tow package wire to red pigtail wire
• Dark Blue tow package wire to blue pigtail wire
• Orange tow package wire is NOT needed
Here's a link to an article you might find helpful:
https://www.etrailer.com/faq-tb-0007-2007-2009-GM-Full-Size-Truck-Brake-Control.aspx
Phil
2/6/2023
Installing 4 wireless security cameras, 3 inside 1 outside on horse trailer. Should I tap into running lights for power or is there a better way to approach this?
Mike L.
2/8/2023
Which camera system are you using? Using the running lamp circuit would be a good way to go versus a switched connection directly to a battery. The install would be more simple, and you'd be less likely to accidently leave the system on and run down the battery because the running lamps would 'remind' you that the system is on.
Mike L.
3/27/2023
@Phil It depends on how much power each camera draws and how much the running lamp circuit on the truck is rated for. Tying in to the running lamp circuit DOES provide a convenient way to power up the cameras, so if that circuit is properly rated, that's the way I would personally do it.
Skyler R.
12/5/2022
I'm having trouble wiring in a new 7 pin plug on my pressure washer trailer. I only have 6 wires: Red White Black Yellow Green and Brown. When I hook the connector to my truck, one tail light comes on, no brake lights and turn blinkers on they all blink. Guess I need to know what the color codes are and if it could be a ground somewhere else. Thanks
Mike L.
12/5/2022
Use a circuit tester like # 40376 on the connector on the vehicle as a helper activates each taillight function. The pinout is shown in the help article I've linked for you. The fact that everything blinks with the turn signals is most likely caused by a poor ground connection. You'll want to check the main ground on the trailer tongue as well as the ground for each lamp to make sure they're securely made to clean metal. If the help article doesn't illuminate things for you (sorry for the pun), let me know and we'll look into it further.
Helpful Links
Skyler R.
12/5/2022
@MikeL thank you for your feedback. I've diagnosed it as old bad wiring and ground. Will be rewiring it this weekend. Once again thanks for the response.
Joe H.
12/4/2022
I have a 6x12 enclosed trailer that all the lights and signals work the way they should. When it's plugged into my 2018 f150 and press the brakes I get the trailer disconnected message. When I let off the brakes I get the trailer connected message. I have found that I have a ground on the brown lead of the wiring harness. I have traced the wiring throughout the trailer but can't seem to find any issues. Any ideas? Thanks
Mike L.
12/5/2022
Explain to me further what you mean about 'having a ground on the brown lead'.... I'll be happy to help through this, but need a little more info.
Justin
1/26/2023
@JoeH this is more of a common ford issue in my experience there is either corrosion or bad connection via the trucks 7 pin connector, i just replaced ours with one from the auto parts store, big metal clips holds the plug into bumper.
Mike L.
1/26/2023
That's a great idea. Check the connection between the tow package harness and the 7-way for green or white corrosion, and replace if necessary. We offer the OEM replacement as part # HM40975.
Helpful Links
Andrew H.
8/2/2022
Hi I have a f150 2018, every time I pull my travel trailer my drunk battery dies. Just finished a long trip during which I had my alternator changed but still ended up with the same problem. Any ideas what could be the problem?
David B.
8/3/2022
Well my friend something is draining your battery. Check the connection posts on the battery to make sure they are not corroded and have good connection. There could be excessive pull/demand on the battery that the alternator can't keep up with. Check your fuses, in some cases a fuse can actually cause an open circuit instead of breaking it or a parasitic drain. There is going to be a lot of troubleshooting involved. Also, the old battery may just have been "done" and need to be swapped out.
Cory E.
7/1/2022
I got a 1973 camper and the trailer plug is gone. Can't figure out the wiring for a new one. It has red green white black wires.
David B.
7/1/2022
Only way to figure it out is to get a circuit tester and troubleshoot it. Get a new connecter and wire it up. Then connect it to power and test the circuits out. Hit the blinkers and brakes to see what function works or doesn't then rewire as needed until you get the right function.
Koreyk
10/23/2022
@CoryE red passenger turn brake, green driver turn brake, black is running lights and white is ground. maybe
Dennis P.
6/30/2022
I work for a paving and excavating company, we have a 32’, dual axel, dovetail trailer w/ 8’ hydraulic lift ramps…the trailer gets pulled by a 2022 peterbilt 567 tri axel dump truck 7 pin connector…I would like to know the best way to set up so when the trailer is being towed it will charge, or at least maintain, the trailer battery for the ramps?? Thanks in advance!
David B.
7/1/2022
Best way is going to be adding a Redarc In-Vehicle BCDC Battery Charger - Single Input - DC to DC - 12V/24V - 12 Amp # RED96FR.
Helpful Links
Joey F.
5/3/2022
Helping my neighbor out. When he connects his trailers flat wire harness to his truck during the day everything works perfectly but come night time when his vehicle sensor comes on to turn on the headlights automatically his trailer lights goes out and stops working.
David B.
5/3/2022
What's up Joey? Let me link you to one of our expert answer pages that talks about a similar issue. I think this will help out. I am also linking to a circuit tester part # PTW2993. If this doesn't help let me know and we can start troubleshooting from there.
Jason
11/27/2022
@DavidB. I kinda have that same problem. 2022 gmc sierra. Re done the wiring on the truck. Today it was still day light out. Finished securing the wires rehooked back up the trailer and now we have no power from the main plugin on the truck to the trailer do note went through with the test light and tested all fuses going to the trailer we have no power on any of the fuses but to let you know on the plugin for the truck we do have power on the battery but no power on any of the other prongs
Mike L.
12/1/2022
That's happening because he has the auto headlight option turned on. If you turn the headlights off and on manually, everything should work okay for you then.
Mike L.
12/1/2022
Hi Jason, I've addressed this in my reply to Joey F. Just scroll down a bit, and you'll see it.
John M.
4/19/2022
I just purchased a 2004 shadow master 6x12 enclosed single axle trailer. I have power at my connection on my truck but I get nothing lighting up on the trailer at all. the harness for the trailer ends up going inside the frame near the tounge. How to I figure out what's going on?
David B.
4/19/2022
Did you try yelling at it and kicking it? That helps me sometimes....Get a Hook Probe Circuit Tester # PTW2993(or something like it) and start testing the wires. Hook up to power and start at the connector testing each wire and work your way back. Since the wire harness goes into the frame I would check all your ground points first before you dig into the actual wire harness.
If you do NOT have a junction box I highly HIGHLY recommend installing one to make life easier for you in the future.
Ben M.
4/10/2022
I installed self-adjusting brakes and when the tow vehicles brakes are activated I can hear a hum from the assembly (which I'm assuming is the magnet activating) but the brakes don't do anything. From an adjustment standpoint the brakes are making contact with the hub when not activated so I think their baseline adjustment is ok. Any thoughts on what I'm overlooking?
David B.
4/13/2022
You should barely hear a little scuff/scrape when you spin the wheel with no power to the brakes. Make sure the magnets are actually engaged when power is applied. Just because you hear a hum doesn't mean they are getting enough power to connect. I linked a couple help articles to walk you through testing the magnets and brakes.
Helpful Links
Gary
10/5/2022
@BenM Im having same problem. Have seven way plug on truck. All lights work great but not brakes.
David B.
10/6/2022
See if this link helps you out Gary, let me know!
Helpful Links
David B.
4/7/2022
2 trailers;both are wired w/4wire conn. I want to add 2" recv.on larger one and tow the 2nd. I need to run 4wire conn. from Ist to 2nd, How and what do I need to accomplish this? Thank you for your time and advice.
David B.
4/13/2022
First make sure you can tow your trailer legally like this. This circumstance will be considered triple towing and there are different rules and regulations surrounding it. All that legal stuff out of the way, I'd say look at # C13701, then take a # 118001 and splice into your front trailers wires to make a connection. If you don't have LED lights you may draw to much power and won't be able to light everything up, just convert some lights into LEDs.
Mike R.
3/27/2022
I want to wire my trailer for tail, brake lights with left and right turn signals. The tail lights only have 2 wires and the wire I bought has 4 wires with flat plug in to truck. With only 2 wires on the tail light, what wires do I use of the 4 coming from the truck
Les D.
3/28/2022
@MikeR your trailer should have at least 4 wires. Green for right blinke/brake light.
Yellow for left blinker/brake light.
Brown for running lights.
White for ground.
I have attached a link that details all the trailer wiring and lighting. If you want to entirely replace your trailer wiring you can use the # 18252 kit with tester.
Helpful Links
Mark B.
3/14/2022
We have a 7 pin harness on trailer. Most lights work ok but the left blinker only works when the right blinker is activated. Right doesn’t activate with left. Brake light is also inconsistent in working. Thoughts on where to start looking. This site and article is super helpful
Les D.
3/15/2022
The first go-to lighting problem solver is grounding. It causes the most problems and unexpected issues.
At the 7-pin connector at the back of your vehicle you will find a white wire that comes off of the back of the connector and attaches to the back of your vehicle. Remove this connection and wire brush the connector lug and the metal attachment spot down to bare clean metal.
The same for the trailer. Near the coupler where the 7-way connector and cable is you will find another white grounding lug. Clean and reinstall it as well.
I have placed a link for troubleshooting trailer wiring below.
Helpful Links
Brent G.
2/21/2022
I have a new Charmac cargo trailer that all exterior lights work properly, but the interior lights will only work if the truck is running??? I want them to be operable with the truck off and keys out out the ignition
Les D.
2/21/2022
Does your trailer have a flat 4-way connector, a round 7-way connector, or other? What about your truck?
Joe W.
12/29/2021
I have a 2017 Ford T150 van with 4/7 connector. When I have any trailer attached, the right turn signals flash really fast on the van, but the signals on the trailer don't work. Running lights, left turns, brakes, all work normal. Is this a ground? fuse? flasher plug? Everything works normal with no trailer attached.
Les D.
12/29/2021
The "hyper flashing" you are experiencing is usually due to LED lights on a trailer. The very low power they draw sometimes fool the vehicle into thinking there is a bulb out.
This is easily fixed with load resistors. For load resistors, I recommend the LED Light Bulb Load-Resistors # DI34ZR. This will include 2 load resistors, one for each turn signal, and feature a durable construction.
Louis H.
12/14/2021
I have a 2011 toyota tacoma with a new T-one harness installed. I have a new 4 pin trailer harness with led lights installed on a 5x8 tilt trailer. Problem is everything works properly with my lights turned off on the truck but with them turned on: seems like the trailer brake lights are on constantly, no turn signals or variance when the brake is applied.
Les D.
12/15/2021
@LouisH these are classic signs of poor grounding or loose wires.
I have attached an exhaustive article that will walk you through all of the possibilities.
First I would check the white ground wire on the back of the trailer wiring harness. File the metal clean and shiny where it attaches.
If you can connect your trailer to a different truck, this will be proof positive that the issue resides on the trailer side or truck side.
Helpful Links
Wendell S.
11/9/2021
I have a 1999 Chevy Silverado I was hooking up a 7 pin connector I have a light green wire coming from my wine out of my truck with no place to hook it to in the 7-pin where does the light green wire hook up to you
Les D.
11/12/2021
I have attached a link that illustrates trailer wiring and connector layouts. The green is usually the right side Stop/Turn signal wire. You can use a tester like # PTW2992 to check its function.
Helpful Links
Matt
10/18/2021
Ok so I have my wires run and ready to connect on my trailer. I am putting in new LED lights and ran a flat 4 wire connector. I know I need to run the brown wire to my black wire, but where do I run the ground wire from the light? The ground wire is only about 8 inches long. And grounds to the tongue. What do I do with the other wire on the light?
Les D.
10/19/2021
@Matt The ground wire on your lights attaches to a grounded metal part of your trailer, typically within the 8 inches of wire that you have. Make sure you attach to a clear bare metal spot. Use a file to clean if necessary.
Heather V.
10/8/2021
I have a 2011 F350 turbo diesel with a factory towing package. It has two 7-way plugs, one in the bed and one under the bumper. The trailer running/tail lights stopped working. When I checked the truck 7-way plug at the bumper, I had power at the pin but no trailer lights. Trailer service checked trailer said the lights all worked in the shop both with testing and connecting to another truck. The next thing the happened was the right trailer brake/turn light was dim, then it went out. I now only have the left brake/turn on the trailer. Please help me, I believe there are several fuses and at least two relays in the wiring harness. I am not sure where to start tracing this problem.
Les D.
10/19/2021
@HeatherV Let's verify your trailer service peoples findings. I guess one quick thing to try is plugging the trailer 7-pin connector into the bed outlet and see if you get any different performance compared to the bumper outlet. If there is a difference it could be a defective plug or poorly wired. It would not hurt to try a different truck, if you can, to make sure we know that the problem is truly on the trailer side or truck side.
Lights not working or working dimly frequently point to grounding problems. On the trailer, just beyond the 7-pin is a white wire that will be screwed to the trailer frame. Take that off, and file the ring connector, and also file to clean bare metal where it attaches to the trailer then reattach and test. Same thing behind the 7-pin on the truck, there will be a white wire there connected to the truck frame that needs to be filed and reconnected. Test again.
If still no power at the truck 7-pin we need to first check the fuses and then trace the power wires back to the source checking any inline fuses we find. Your owners manual will tell you which fuses in the fuse block are for trailer lighting.
I have attached a document showing trailer wiring and which pins do which lights. Remember, you will need to have truck lights on to check running lights on the trailer, and flashers on to test turn signals.
A tester like the # PTW2993 will make testing pins and circuits easier. See the attached video that shows how to use it.
Aj P.
9/28/2021
I got a older haulmark elite 2 race trailer. 7 pin plug. Hooked up everything. Bought new lights for it because I thought the old ones were bad because they didn’t work. All the wires under the trailer seem fine. Has a battery for electric breaks. Do I need a new battery for the brake lights and running lights to work. No lights or anything work on this trailer
Les D.
10/19/2021
The battery on your trailer could be for accessories inside your trailer like overhead lights, etc. A small battery on your trailer could also be for "breakway brakes" that only engage if your trailer comes loose from the tow vehicle while driving. The power for your electric axle brakes, running lights, brake lights and turn signals come from the tow vehicle.
First determine if the problem is with your tow vehicle or the trailer. You will need a tester like the PTW2993 circuit tester. then consult the attached document for what to measure on each of the 7 pins on the connector. If you do not have power at the 7-pin then the problem is on the towing vehicle. Check the ground wire that is is connected to a clean bare metal place on the frame. Also file the ring connector to ensure a good connection. If that does not resolve your issue then you will need to trace the power wires to the power source checking any fuses you find along the way. Also check your owners manual for which fuses in the fuse block support the trailer lighting.
If the problem is on the trailer side check for power at each of the lights. If you have power but no light, check the ground wire or the bulb.
I suggest trying all of these options before installing any new lights.
Helpful Links
Carlo N.
9/28/2021
I have a 28ft toy hauler, I put new brakes on &now I have a problem no brakes.
Les D.
10/19/2021
@CarloN It sounds like you forgot to reconnect the ground or power wires. Each electric brake has two wires. One wire for 12-volt brake power and one for ground. All 12 volt brake lines connect to each other and at the front connect to the 7-pin wiring on the braking line. All of the grounds connect to the grounded metal part of the trailer. The wires coming off the brakes have no polarity so you can use either for power or ground as long as all grounds come together and all power lines come together. I have attached a document on trailer wiring that has a good illustration of this. Let me know if this works for you.
Helpful Links
Bill J.
9/26/2021
I have a new to me, 1995 2-axle, 2-horse WW trailer. It has the standard 7-pin connector and electric brakes. All the lighting work, however, the breaks become engaged as soon as the vehicle key is turned on. I've connected the trailer to two different vehicles with the same result. Somehow the breaks are getting voltage to engage even when the break petal is not pushed. Now i can't pull the trailer because the break system is always "on". Any thoughts on what's happening?
Les D.
10/19/2021
@BillJ I would start by testing the wires on the 7-pin connector on your tow vehicle. Use a # PTW2993 circuit tester. Most frequently when people have this issue we find that the electric brake line has been swapped with the 12-volt accessory line. The circuit tester will easily show you this. I attached a video that shows how to use this tester, and a document showing how trailer wiring at the 7-pin connector should be.
Mokp
9/23/2021
I have a big Tex utility trailer and with a seven plug connector and whatever it drives it appears that the brakes are on I looked at the wiring underneath and somebody has connected the ground to the power for the brakes what the hell is this a standard configuration or what can I do about it
Les D.
10/19/2021
I have attached a document that illustrates standard trailer wiring. It also includes a good illustration of the trailer break wiring.
Electric trailer brakes each have two wires on them. One for ground and one for power. Brake wiring does not have any polarity, so either wire can be used for ground or 12-volt, as long as all 12 volt wires run to the brake wire on the trailer, and all the ground wires run to ground. Typically the ground wires attache to the trailer frame near the brakes, while all 12-volt wires are tied together and run to the 12-volt connection on the trailer.
Finally, your 7-pin connectors have a blue wire for the trailer brakes. The also have a pin for 12-volt accessories. Make sure these have not inadvertently been swapped. If they were, the brakes would be on all the time.
Helpful Links
Danny S.
9/1/2021
Hello. , I have a typical 2008 6x14 enclosed trailer , all the lights work great when plugged into my 2011 Tahoe but only 1 brake light and 1 blinker works when plugged into my 2001 Silverado 1500. , using the same adapter to each vehicle. Are these vehicles wired differently ?
Victoria B.
9/7/2021
@DannyS These vehicles would not be wired differently with factory wiring. Vehicle wiring is standard so that it will work with all kinds of trailers without the need for tons of different adapters. The colors used for wires on trailer wiring may vary, but trailer connectors are wired the same by function. I would use a circuit tester on your Silverado's trailer connector to make sure that all of the light functions are working correctly at the truck's connector. This will help you narrow down the issue. Since the trailer works correctly with your Tahoe, I am inclined to say that the issue is on the Silverado. It may be corrosion in the connector or one or more blown fuses.
Manny R.
8/20/2021
I have a 2014 GMC Yukon, 7 pin factory plug. I bought a trailer wired for 7 pin with an electric hitch. The electric hitch does not work on my truck but works on the truck the previous owner had, I believe it was a Toyota. Can someone point me in the right direction?
Victoria B.
8/26/2021
It is highly likely that the power wire on your Yukon need the final attachment made under the hood so that the 7-way actually has 12V power. I have linked a help article that talks about this issue and covers how to make the necessary connections in the "solutions" section.
Darrell M.
8/19/2021
I connected a new 7-way to my truck for my trailer and brakes however now when everything seems to work but my running lights stay on after everything is off the keys off and they do not turn off I can unplug the main plug the tail lights will go off but if I turn the lights back on the tail light stay on again. And I'm using all standard bulbs no LEDs
Victoria B.
8/23/2021
I would check all of your grounds to make sure they are secured to bare, clean metal. Sometimes if a ground location has some corrosion or something like that it can cause a short and pull power though the connector. I would also check your trailer connectors to make sure they don't have any damage, corrosion, or bare wires touching that could be causing a short to draw power on the taillights even when the truck's lights are off. If everything seems to check out, a battery isolation solenoid may do the trick.
Darrell M.
8/24/2021
@VictoriaB
Thanks,
It ended up being the new 7-way. Rare but they are not always the best money can buy, even when it's a Hopkins. Of course now my brakes on the trailer are locked up when I connect my trailer to the truck.
Matt W.
8/17/2021
I have a travel trailer and a utility trailer and I am towing with a 2019 tundra. Both have a 7 way plug. Towing the travel trailer, everything is fine. Whenever I am towing my utility trailer it constantly shows the trailer comes disconnected. This is most annoying. I have traced it down to the trailer brake system, but was unable to figure out anything from there. I notice above it shows different wiring configs for RV and Utility. Could this be the issue? I have noticed it one other time when towing another utility trailer? Is there an adapter, that I can use to eleviate this issue?
Victoria B.
8/19/2021
7-Way Traditional and 7-Way RV-Style connectors are wired in the same configuration but use different wire colors to indicate wire function. If your trailers are wired traditional vs rv-style, this should not be causing your "trailer disconnected" issue. Have you checked your utility trailer's connector for signs of wear and/or corrosion? Sometimes these issues are cause by a weak connection at the trailer connectors and as you drive down the road the connection comes and goes. I would also check the wire connections at the rear of the trailer plug (if accessable) to make sure the brake wire isn't working its way out of the connection point. If you find the connector is clean, let me know and we can try and troubleshoot further from there.
Wayne F.
7/30/2021
I have a 2008 TAB trailer that has a 7 pin connector. When hooked up to a vehicle with 7 pins all lights work correctly. I have a 1994 Chevy pickup with 6 pin and a 2015 outback with a 4 pin. Using a 6 pin to 7 pin or a 4 pin to a 7 pin brake lights ok, left turn signal work ok. running lights ok. Right turn signal all lights are blinking on the trailer. What can I look for?
Victoria B.
8/4/2021
My first instinct is to check the light grounds. When there is a ground issue, the trailer lights can behave oddly, in ways that don't make sense. I think maybe when you're connected to your tow vehicle with the 7-way, the lights are getting a sufficient ground possibly through the 7-way connector. I'm thinking the two adapters don't provide the same ground connection and are possibly causing this issue. I would check the ground at the right-side lights that are acting up, as well as the trailer's main ground.
Fidel B.
7/19/2021
By screwing the connection box of my 7 pin wire under the clip of my fifth wheel m I crushed a wire and there was smoking, so I closed the master switch of the battery. The 7 pin cable was not connected after my pick up. My q question is it would be the wire of the brakes that I would have to pierce with the aim which would have caused a short circuit. Thank you for your good advice,
Jon G.
7/20/2021
While our charts show what the typical wire colors are for trailer wiring, there isn't a law saying they have to be that color so you'll just need to test each wire to see what function it carries.
Jim N.
7/6/2021
I have a 2019 GMC Seirra Denali and I bought a new car hauler. The problem is I bought it about 200 miles away and the left signal light dosen't work. Since it would cost more to haul it back than pay someone to repair it. I have checked all the connections I can find and checked the bulb all are fine. Any help will be appreciated.
Jon G.
7/8/2021
Have you checked the fuses in your pickup? Attached is a link to our helpful article about troubleshooting wiring that you can check out.
Helpful Links
Al
6/16/2021
What a great article very informative. I do have a question. I am switch my old rv tail lights to a led tail light. Upon looking at the wiring it has 4 wires coming out hooked to old light. New light has 3 wires from partsam light. I am going to systematically test each to find out what works what. But does any of those effect my trailer brakes, like if I hook them up wrong? Because I’m going to have to combine 2 of the wires together so they can connect to one of the three wires? Right help!
Jon G.
6/22/2021
First just to clear the air, your trailer brakes are on a different circuit than your lights so you can rest easy there. When it comes to different amounts of wires what we normally see is that one of the lighting units uses the mounting hardware to ground while the other one used a wire. Testing your wires per function is the absolute best way to make sure you have everything hooked up correctly.
John B.
11/24/2024
@JonG hi my 7 plug hookup on my gooseneck trailor got ripped out by accident I purchased a new one and have everything wired back up unfortunately now my running lights on my trailor are staying on even with all the other lights turned off. Any suggestions would be greatly appreciated. Thank you in advance.
Jon G.
11/25/2024
@JohnB When you installed your trailer 7-Way did you match the wire colors, or the wire functions? A common mistake is to just match the colors and call it a day, but wiring manufacturers will use different colors so it's very possible that you've simply connected the running light power pin for your trailer in the same location as the 12V power for your truck. I recommend double-checking which functions are connected where as a starting point.
Plumberjohn
5/24/2021
I have a 1973 slide-in truck camper. I'm trying to connect the electrical pigtail from my 2002 Chevrolet Silverado. The slide-in truck camper had a 6 Pin round (male), and the truck has a 7 Blade round (male). Is there an adapter or cable to make this possible? I'm not able to determine what pin does what on the slide-in truck camper. Any advice is greatly appreciated! Thanks!
Clifford B.
5/23/2021
I have a 2009 Ford F 150 with the 7round plug and a 4 flat wire plug I can use either one just bought a new set of magnetic lights with red and orange lens and already have the led lights mounted in the trailer only all lights work when head lights on truck are turned but no brake or turn signals I have a 7 pin to flat 4 round connector why is it that the lights work but not the brake or turn signals
Jon G.
5/25/2021
Have you checked to see if you're getting a signal on those pins without the lights connected? It could be that you either need to replace some fuses in your truck or that you have a bad set of magnetic lights.
Gary S.
5/16/2021
I have a Wells Cargo Auto Hauler trailer. Originally in the black box that houses all the connections (located on the front tongue) there was a diode in-line with one of the wires. My friend borrowed the trailer, and somehow burnt out (melted!) the wiring. Now the back up lights on my 2006 Dodge Ram 3500 stay lit when I plug in the 7 blade connector. How can I fix this, or what part/wiring kit do I need? Much tanks.
Jon G.
5/17/2021
I would replace what you currently have with a completely new box like part # 38656 along with the 7-Way Molded Trailer Wire Connector part # H20043 so that you can get rid of the bad wiring. I'm not sure what wire that diode is on but I would also try to figure that out and replace it with a higher-end diode like part # RM-690 if it was a single-light diode.
Jim S.
5/15/2021
I have a 2021 VW ID.4 which come pre-wired for 7 pin connections, while the kayak trailer on has only 4 pins. What solutions are there
Jon G.
5/17/2021
I would look into either using an adapter like part # C35FR which just plugs into your 7-Way or by using a completely different connector like part # 30955 which plugs into your US Car Connector (when you unplug your current 7-Way from the back). This gives you both a 4-Way and a 7-Way so that you don't have to keep track of an adapter.
Jake W.
5/8/2021
the 2003 ford psd wire colors are not the same as you are claiming. at least on my truck. i know. im trying to rewire a new plug in right now. keep blowing fuses.
Jon G.
5/10/2021
The colors that we mention are just standard wire colors but they don't always match in real-world applications. As you've found in your situation you'll want to test the wires per function instead of just going by the color.
Shannon
5/5/2021
How can I run a 12v fuel pump into a 7 pin and control the power from a uplifter switch in the cab of my truck Ford F-250 super duty
Jon G.
5/6/2021
I'm not sure how you would make the connection to your uplifter switch and you would want to make sure that you have a circuit breaker or fuse to protect it, but what I would do is run 10 gauge wire # 10-1-1 from your uplifter switch back to the 12V power pin on your 7-Way which would be the pin in the 1 o'clock position .
Steve
5/3/2021
I have a 2020 G M C truck I wonder can I use the light wire to charge my battery to my power winch it a lawn mower battery ? If I turn my lights on while running ? That the flat 4 plug .
Jon G.
5/4/2021
The 12V power wire struggles enough to charge a battery with a 10 gauge wire so the smaller 16-18 gauge wire used for your trailer lights will not be nearly large enough to give your trailer battery a trickle charge. Your truck should have a 7-Way socket as well so all you should need to do is install a 7-Way on your trailer and route the power wire to your trailer battery. I recommend the junction box # 38656 along with the 7-way molded wire connector # H20043 because it will help keep your wiring organized and make future repairs or modifications much easier.
Ben
4/30/2021
Without turning the mini van on I have full lights on, brake, left and right work perfectly. New cable harness. I need to disconnect the trailer connector to kill the running lights. Any ideas
Jon G.
5/3/2021
It sounds like you have LED lights on your trailer. LED Lights are nice because they don't require as much power to operate but as a result sometimes they will light up dim when there is the smallest amount of power on those circuits. If you use a resistor like part # C57003 for a 7-Way setup or some that you install on the wiring directly, like part # DI34ZR, it should take care of your problem.
Bob C.
4/20/2021
Hi. What is the best way to add a third brake light on a camper shell mounted on a 2002 GMC Sonoma SLS? I have a junkyard rescue shell that does not have a third brake light and will mount an aftermarket LED but I am not sure if a hot wire is available. Just need advice from more knowledgeable folks
Jon G.
4/22/2021
Sometimes there will be provisions for 3rd brake light wiring somewhere along the frame but from the research I've done in the past it seems like there is no rhyme or reason as to which trucks have this wiring and which trucks don't. The best solution I have for you is to install the 3rd Brake Light Logic Module # PP20-702. This is a very straightforward installation and will give you that brake signal that you're needing.
Edward R.
4/18/2021
Hi! I have a 2012 RAM 1500 quad cab which has the standard incandescent lights. I’m building an Wind Stream 24ft utility trailer with LED LIGHTS. Question is “Do I need to have a converter to control the return voltage to control and protect the fuse panel in the truck?”
Jon G.
4/20/2021
If you don't have the factory 7-Way and you're just wanting to install a 4-Way flat trailer connector for the trailer lights then I wouldn't say you HAVE to have a converter, but it does help to protect your truck so I do recommend using a wiring kit that comes with one like the part # 119178KIT.
Craig W.
4/16/2021
I need to wire a four flat to the back of my camp trailer in order to connect to small aluminum trailer which already has a four flat. Any advice on this project would be helpful.
Jon G.
4/20/2021
You can try to tie that into your current trailer wiring with a 4-Way flat like part 18252. One thing to be mindful of is that this will pull more power on those trailer light circuits so you might see problems there if there is too much power being pulled.
Gordon S.
12/11/2021
@JonG if you still need to finish this project, might I suggest you run a four wire flat extension from the front off the travel trailer to rear along the frame and connect the small aluminum trailer to it. Use a Y-splitter at the truck tailgate and power both trailers independently.
I was unable to post a couple of photos for reference.
Google 4 Way Flat Y-Splitter Plug and Play Adapter Extension and
Trailer Wire Extension, 20ft, 4-Way 4-Pin Plug Flat 20’ Harness Extender
Good luck.
Matt S.
4/2/2021
Is there a ASME, NEMA or other standard that controls the pin diameter and spacing of 4-flat plugs? I have several trailers with 4-flat plugs and the spacing and diameters, while similar, do not appear to be the same, which makes it difficult to plug into some and loose connections on others.
Jon G.
4/3/2021
I don't think there is a specific standard when it comes to the spacing and sizing for the 4-Way flat plugs - I think it's more of a "make your plug to fit like this so that it works with everyone else" sort of thing. You definitely aren't alone with this situation, which is why Hopkins came up with their Easy-Pull Harness that has a ring in the middle of the connector that makes it easier to remove when you need to. For a trailer end piece use part # HM48114 and for the vehicle end use part # HM48044.
Butch
3/29/2021
I have a 2001 Ford f250 super duty truck, I just purchase a sure trac enclosed trailer and moved to Florida. All the lights work on the trailer however I cannot get the Interior dome lights to work. I watched a you tube video to where a man said that his Chevy truck did not have the fuses installed in the fuse box, can anyone tell me what fuses I need to check and have installed? Any help would be appreciated.
Jon G.
4/2/2021
You should be able to find this location in your copy of the owner's manual. When I looked online I believe the fuse you're looking for is in location 16 and is labeled as "Trailer Tow Battery Charge" and it sends back 12V power. You'll want to confirm this on your end too.
Willie J.
3/28/2021
Hey, I just brought a used Carry-On trailer with a 7way flat and it have three wires on the left side and two wires on right side running from the rear for clearance marker and tail lights . With only one oval LED fixture at rear on each side. Do I need a 5 to 4 converter? My truck is 2010 Ford F-150 with turn/brake is feed from the same wire.
Bill F.
3/25/2021
Need to go from 4 wire flat on motorcycle to 9 wire round on a can am motorcycle trailer. It is a 2018 Honda motorcycle.
Kef G.
3/25/2021
There aren't any 4-way to 9-pole adapters, so the best way to get this working is to splice a 4-way into your trailer and remove the 9-pole.
Drew M.
3/16/2021
I have 6 wires going into a 7 wire plug. None of the wires are blue and my electric brakes do not work. The only blue wire I see goes to a junction box on trailer w/black wire. How should I wire the plug? Should the black act as the blue wire? Very frustrating
Jon G.
3/18/2021
While this article shows industry standards, it isn't a hard and fast rule. It sounds like you'll need to test the functions of all of your wiring and make your connections per function instead of per color.
Richard H.
3/14/2021
I am rebuilding an old aluminum trailer and have purchased new replacement sidemarker lights. Because the metals react to each other and corrode, I have put a silicone gasket between the two metals. Will this cause a grounding issue? I have done the same with the new taillights. Thx!
Jon G.
3/15/2021
If the grounds for the lights are not able to make contact with the trailer frame then yes, that will cause issues. To try to avoid the corrosion you're talking about I would try to ground all of the lights to a main ground line and route that up to your trailer connector.
Dan O.
3/6/2021
Question, not sure if this is the correct location to ask a question. But here it is. I have a 1982 Sunline camper trailer. I replaced the standard bulbs with new LED tail and running lights. Their was green and white wires at running light locations. Here’s the issue, when the running lights are OFF the turn and stop lights work fine. When the running lights are ON the turn and STOP lights DO NOT work.
Jon G.
3/8/2021
Sounds like you either have a bad ground or short in your wiring. Check and make sure that all of your wiring (on both sides of the towing setup) is in good condition and that all of your grounds are secured to a clean, bare-metal surface. Attached is a link to a tiring troubleshooting article that you can check out.
Roger K.
4/10/2021
@DanO I also ran into a simular problem with my vehicle when I converted to LED lights. I found the problem to be that the vehicle had a negative switching system which does funky stuff to the lights. I wired in relays to convert the negative switching to positive switching now I am having no issues.
Emmanuel A.
3/2/2021
Hi there a have a small car dolly 7pins plug and the colors the my has is yellow Lt, white GD, green Rt but i am confused theres is one wire yellow/brown and green/brown i dont know what terminal are those TM or EB or AX. I need some help please. Thank you
Jon G.
3/4/2021
What you're going to need to do is apply 12V power to those wires and see what happens when you do that. Brown is typically used for running/tail lights so that might be where those wires need to go, but you also need to make sure that you have the stop light covered as well (which is typically on the same circuit as the turn signal). The one annoying thing about wiring is that there are typical colors but it isn't an industry standard that everyone has to follow. This means if something doesn't quite match up (like what you're experiencing) then we need to do the testing.
Dave H.
1/28/2021
I really don't like the Idea of "showing" electric trailer brake wire being grounded to the trailer axle. My axles move and is some what going to have a voltage drop when finding ground. My preferred method is to connect to the ground wire and keep the frame ground out of my schematics. By adding undetermined amount of resistance to the brakes you may end up with each wheel or at least each axle getting a different current flow and uneven braking. Thank you for having all this information quick and easy to find.
Gordon S.
12/11/2021
@DaveH I agree for the most part.
Just rewired a small utility trailer with a tilt feature with LED lights. I ran a separate ground wire down each side of the frame for each marker light and taillight from the same point I grounded the connection at the tongue.
This way it does not rely on a ground at the pivot point, the lights maintain maximum power constantly.
Show All(102) Replies
Hide Replies
Explore Expert Info
![Our Expert]()
on Wiring
on Wiring
Videos
for Wiring
Help Articles
for Wiring
Expert Answers
for Wiring
Most Popular Wiring Videos
Most Popular Wiring Articles
Most Popular Wiring Expert Q&As
It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…
view full answer...The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…
view full answer...That's a very good question, we tend to be extra cautious and say to use 10 gauge wire because that would be more than enough. When you get into longer trailers that will end up using a lot of wire the heavier gauge wire becomes more necessary.…
view full answer...Since wire color codes are NOT universal, we always recommend wiring by function, rather than wire color. If you look at the Trailer Wiring FAQ article I have linked you to, you can see some diagrams showing the proper way to wire a vehicle and…
view full answer...When wiring a trailer connector, it is best to wire by function, as wire colors can vary. We have an excellent wiring diagram on our website, I will provide you a link so you can look at it. If you are looking at the inside of the trailer connector…
view full answer...You have it right so far, the 4-way connector is just as you have stated. Remember that Yellow has a L in it so that is the left side brake/turn signal and green has a R in it so that is the right side brake/turn signal. The colors for wiring a 7-way…
view full answer...Hello David, thanks for reaching out. If you asked me this a year or two ago, I probably would have told you the Advent unit can replace a Carrier unit. That said, there have been a lot of changes to RV AC units in the last year or two and we have…
view full answer...If your trailer has 7 wires running all the way back to the brakes, then yes, you can tap into the existing wiring. Each of your new brakes will have two wires for the brake magnet. One wire is for 12 volt power to the brake magnets and the other…
view full answer...Each lamp needs to be grounded either through its mounting studs being in direct contact with the trailer frame or by having a jumper wire ran from the lamp to the trailer frame. Ground the trailer connector at the front of the trailer, which will…
view full answer...It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…
view full answer...Your 4-pin/5-wire wiring harness is what is called a "wishbone" type which simply means that there are two separate running light wires, one brown and one pink. This allows a separate running light wire for each side of the trailer which…
view full answer...Going by the colors that you mentioned, it sounds like you have the typical set-up, green wire for right turn and brake, white wire for ground, yellow wire for left turn and brake, brown with green wire for right side running lights, and brown with…
view full answer...Departments
Towing
- Trailer Hitch
- Fifth Wheel
- Gooseneck
- Towing a Vehicle
- Front Hitch
- RV Hitch
- ATV Hitch
- HD Truck Hitch
- Vehicle Wiring
- Brake Controller
- Ball Mounts
- Weight Distribution
Sports and Recreation
Trailer Parts
- Utility Trailer
- Boat Trailer
- Landscape Trailer
- Enclosed Trailer
- 5th/Camper Trailer
- Car Hauler
- Horse Trailer
Vehicle
Contact & Help
What our customers are saying:
"The best service I have ever received from any order I have ever placed online."
Elliott
Mountainair, NM
Don B.
10/17/2025
Trailer and lights have working fine. Now all of a sudden when I back up my car trailer I notice that I'm pushing the trailer backwards. Brakes are applied. Pulling trailer forward seems to be ok