Troubleshooting 4 and 5-Way Wiring Installations

Wiring issues can be frustrating and time consuming to fix, especially when you are not sure where to begin troubleshooting. When your trailer lights aren't working, your trailer is not working, and you are losing valuable time and money. Using the following information and testing procedures, you should be able to locate and eliminate the most common issues encountered during or following a 4 or 5-Way wiring harness installation and get back on the road as soon as possible.

Where to Begin

When it comes to troubleshooting a wiring installation, testing is everything. A lighting problem can originate at any point along the wiring on either the tow vehicle or the trailer, so it is important to determine not only what is causing the problem, but where it is located. The question the troubleshooter will find themselves asking is "There are so many things to check. Where do I start?"

Vehicle and Trailer Wiring Systems

Perhaps the most helpful thing you can do to start troubleshooting is to determine whether the problem is on the tow vehicle or on the trailer. When you use your trailer to test, you have no way to know for certain whether the problem stems from an issue with the wiring harness because the trailer's wiring system is still part of the equation. Testing the vehicle without the trailer will allow you to separate the wiring system into manageable sections.

Use the testing procedure described in Method 1 to check for function at the vehicle's 4-Way plug. If all the functions come out correctly at the vehicle plug, you will know that the problem only appears when the trailer's wiring system is connected and you can concentrate your efforts on the trailer.

Troubleshooting Tool Checklist

What Tools Do I Need?

The most helpful tool to use will be a 12V probe-style circuit tester. Click here to see our circuit testers. In addition, you will want to have basic wiring tools on hand. These include electrical tape for repairing connections, a wire stripper for cleaning up wire ends, dielectric grease, and various wiring fasteners like butt connectors, quick splice connectors, or ring terminals, depending on the type of repairs required. Wiring kits that include these items are available.

A trim fastener removal tool can reduce the time needed to access your tail light wiring, particularly in SUV and minivan applications, but a flat-head (slotted) screwdriver will often work just as well. A power drill will be used to install the screws for the ground wires. A 12V battery can also be useful for testing trailer lights in situations where you don't have access to the vehicle or you suspect an issue with a particular trailer light.

Common Wiring Issues
Problem Possible Issues Testing Procedures
Trailer lights work except for one function: brake, right turn, left turn, or tail.
  1. Harness wires are not connected to vehicle correctly/securely.
  2. (Plug-In Only) A set of connectors is not seated together properly or is not making a good connection.
  3. (Plug-In Only) A required fuse or relay is blown or missing.
  4. (Hard Wire Only) Vehicle has separate turn signal and brake lights, brake wire is not connected.
  5. Insufficient ground or short to ground on trailer or vehicle side.
None of the trailer lights work for any functions.
  1. (Powered Converter Only) 12V power wire is not connected to vehicle battery.
  2. (Plug-In Only) Harness is made for models with a factory tow package, vehicle does not have tow package installed.
  3. (Plug-In Only) A required fuse or relay is blown or missing.
  4. Harness does not have a connection to ground.
  5. Harness has been overloaded.
Trailer lights worked when the harness was first installed, but eventually stopped working on one or all functions.
  1. Ground location for harness or trailer connector is weak or ground connection has loosened over time.
  2. Harness has been overloaded due to excessive draw from lights or a short in the trailer wiring.
Using one turn signal engages the turn signals on both sides of the trailer.
  1. (Hard Wire Only) Vehicle has combined brake and turn signals, brake light wire on harness is not grounded.
  2. Insufficient ground or short to ground on trailer or vehicle side.
Turning on head lights in the vehicle causes one or more of the trailer lights to stop working.
  1. Insufficient ground or short to ground on trailer or vehicle side.
  2. Harness is overloaded when tail lights are engaged because the trailer has too many running lights.
One or more functions stays turned on, even when the vehicle ignition is off.
  1. (Hard Wire Only) Incorrect connection to vehicle wire.
  2. Insufficient ground or short to ground on trailer or vehicle side.
  3. Harness has been overloaded.
  4. (Powered Converter Only) Trailer has LED lights which can be powered by the low-level residual voltage present at the 4-Way plug.
Harness functions correctly at the vehicle side 4-Way plug until trailer is connected.
  1. Insufficient ground or short to ground on trailer.
  2. Harness is being overloaded when trailer is plugged into vehicle.
(5-Way Only) Trailer reverse lights or reverse lockout function are not functioning.
  1. Fifth wire from harness is not attached to reverse light circuit on towing vehicle.
  2. Insufficient ground or short to ground on trailer.

Basic Testing Procedures

Testing the 4-Way Plug

Method 1: Testing for Function

At The 4-Way Plug

Testing Behind the Converter Box

Behind the Converter Box

Verifying Wire Connections

Method 2: Verifying Correct Wire Connections

Hard Wire Installation

Trailer Wiring Color Code
Connector Function Harness Wire Color Where To Attach - Vehicle Side Where To Attach - Trailer Side
5-Way 4-Way Right Turn Green Vehicle's right turn signal Trailer's right turn signal
Left Turn Yellow Vehicle's left turn signal Trailer's left turn signal
Ground White Vehicle ground point - metal, uncoated, rustproof Trailer ground point - metal, uncoated, rustproof
Tail / Marker Brown Vehicle's tail light circuit Trailer's tail lights
Reverse Blue Vehicle's reverse light circuit Trailer's reverse lights or electric lockout solenoid
This chart is a typical guide; wire colors may vary based on manufacturers. Use a circuit tester to verify connections.

T-Connector Installation

Plug-In Installation

Grounding the Harness Separately

Method 3: Checking Ground Connections

On the Towing Vehicle

Trailer Ground Locations

On the Trailer

Fixing Damaged Wiring

Method 4: Finding Other Possible Issues

Method 5: Checking for an Overload Situation

Amperage Draws for Common Trailer Lights
Incandescent Light Tail Light Circuit Stop/Turn Circuit LED Light Tail Light Circuit Stop/Turn Circuit
.5 amps 2.4 amps STL70RB
.054 amps .362 amps
1 amps 2.5 amps STL9RB
.062 amps .259 amps
.9 amps 2.3 amps STL17RB
.121 amps .279 amps
.2 amps N/A MCL44RB
.054 amps N/A
.2 amps N/A MCL44AB
.054 amps N/A

For more information, see:

Updated by: Raymond P.

Last updated: 7/6/18

Questions and Comments about this Article


I installed a CURT mdular in my 2007 Ford Escape. I tested the lights on truck side and I am getting constant power on the brown lead, flask of the yellow but nothing on the yellow. Note when all lights are off my test light stays lite on the brown wire. I have plugged into my trailer and it blue a fuse after I touched the breaks, only one side worked.. please help 105851

Reply from Jon G.

What wiring harness did you purchase for your 2007 Escape? It sounds like you either have wiring problems on your vehicle, you got the wrong wiring, or the wiring itself is bad. 76484

Reply from Steve

@JonG It reads in the instructions that if using the converter as a powered module for a two way system, the red brake wire must be grounded. Have absolutely no idea how that works. The system from Curt is the 56345 for a Ford Escape 2007 76499

Reply from Jon G.

The Curt T-Connector # C56345 is a fit for your 2007 Ford Escape, but I'm not seeing that note about the red wire anywhere in the instructions. I know for some of the universal wiring systems (that you splice in) will sometimes have a red wire for if your vehicle has a separate brake light and in that case you would ground the (normally) red wire if your taillights had the brake and turn signals combined. For this wiring kit you should tee in the connections behind your taillights, ground the white wire, and route the black wire up to the positive post on your battery. You might want to take a look at the installation instructions linked to our product page to make sure they are the same as what you have. 76539

Ethan C.

I got a 08 tacoma trd sport. Got some after market tail lights and to do some splicing. Here's where I got confused. On the truck there's a green with red striped wire, all green wire, and a black with white wire. The after market wires (Only 3 wires) are all black with the letters A,B,G. Now my left taillight isn't working unless you press the brake. Any advice on where I went wrong? 105302

Reply from Jon G.

I think what happened is that you mis-wired something. You'll need to figure out what wire is for what function on your taillights as well as the aftermarket wires and splice them together accordingly. Most people get lost in wiring by trying to match colors when it's more about matching functions instead. So match per function and be sure that you have a clean and secure ground connection - this should resolve any problems that you have. 76200

Reply from Ethan C.

@JonG I got it down. Works perfect but have to get a new battery. Thanks again 76218

Reply from Jon G.

@EthanC Glad you were able to get it working! 76219

Ken L.

I installed the unit a little over 4 years ago but never connected it to the battery. I did so today and hooked up the boat. Passenger side is fine. Nothing on the driver side. It got to the point that I stripped a little insulation ahead of the sending unit. Good there. Did the same on the other side. Nothing. Probably nothing I can do short of replacement of the entire harness? My fault for not checking sooner but the real bummer is the time to put in a new one right now especially given weather conditions here. :( 103234

Reply from Jon G.

If you're talking about the wiring on your tow vehicle and the "unit" being a module then you definitely tested correctly and it sounds like the module is bad. Most wiring warranties would have been up by now so it does sound like you'll likely need to just replace the whole unit. 75746

Dave A.

Turn and brake lights r fine. But tail lights quit. Put a tester on vehicle / converter side and brown wire / tail light wire is always on, even when car is off. Help me? 103037

Reply from Jon G.

Start by checking any fuses or relays for the trailer tail light function and then move on towards the wiring itself (including the grounds). It might be that some wire is damaged and is touching another wire that has constant 12V power. 75677


Hi , when i use the 3 light tester on my truck trailer conection it light ,tail,r-turn,l-turn ,brake ,,as soon as i conect to my trailer im loosing power in the wireing and no trailer light , do you know wy 102400

Reply from Jon G.

If your truck side is testing just fine then it sounds like the problem is on your trailer. I'd start off by checking all of the grounds for your trailer lighting. Make sure that your grounds are securely connected to a clean, bare-metal surface and that there is no corrosion or even paint between the connection. 75373

Reply from Gino

Hi Jon, thank for reply, but its not the trailer since when i conect my other truck all the light works on the trailer ,and not on this truck ,funny thing is when i put the 4pin tester on the truck its woks ,as soon as i connect to the truck i lose power in the wire ,even in the truck arnes 75375

Reply from Jon G.

@Gino If that's the case then you'll want to check the grounds on your problem truck. It would also be a good idea to check the connection of all of your wires to your truck's 4-Way connection to make sure that they are all secured with a clean connection. 75378

Reply from Jeff B.

@JonG I am curious if the grounding wire connection to an all aluminum trailer is the same as one for steel. My trailer is all aluminum and all fasteners are stainless steel, grade 312 u Bolts and straight bolts. The connection of a ground wire, for the bar lights at the back crossbeam after 2 years of operation was completely eroded from the aluminum frame. Thinking galvanic corrosion. I do use Salt Away every time I pull the trailer out of the water. Thoughts? Do I need a separate ground wire back to my truck? Thank you 76095

Reply from Jon G.

@JeffB While aluminum is a conductor, it's not quite as goo as steel is when it comes to a reliable ground connection. If the coupler on your boat trailer is steel then I'd try running any ground connections up to the coupler and using a self-tapping screw to establish a better ground connection. 76106

Reply from Jeff B.

@JonG What I discovered was the ground connector to the steel coupler was completely eroded away. The ground connector from the right lamp was also completely destroyed and caused corrosion on the surface of the aluminum trailer. Placed a jumper wire in line and reconnected, all good. I'll be rewiring it all next week. Thank you 76112

Reply from Gino D.

@JonG hi just to let you know , about that trailer/truck problem i had , i found the problem and all that time it was wire corrosion on the wire harness from my truck from not having a cap at the end where the pin are ! so the corrosion when up the wire all the way and as soon as i place an extra charge on that harness the voltage was going from 12 v to 1.5 v an was anough to light the tester but not anough to light the trailer ,, thank you for your recomandation do 76116

Reply from Jon G.

@JeffB Yup, that'll do it! Glad you were able to figure it out! 76135

Reply from Jon G.

@Gino No problem! Happy to hear that you were able to find the issue. If you still need a 4-Way connector then I'd go with the Hopkins Endurance # HM48058 because it comes with a built-in tester, a cap, and their easy-pull harness for an easier way to disconnect your trailer 4-Way. 76136

A.r. M.

Is it possible to kill a powered converter if the ground is bad on the vehicle? The trailer lights worked, then stopped after one outing. After fixing the ground to a solid connection, I have 12V to the running lights and insufficient (low in range of 1-3V) voltage to the brakes and signals. The trailer lights work properly behind another vehicle. 101517

Reply from Jon G.

It's definitely possible to damage the converter box if something isn't wired correctly, but I would double check all of your connections before ruling that it's the converter. I would imagine that you wouldn't be getting any voltage at all as opposed to getting low voltage to be honest. 74948

Reply from A.r. M.

@JonG Thank you for the reply. Instead of trouble-shooting behind the converter, I followed my gut and elected to replace it with a Curt harness from your site. The previous install was by a local U-Haul dealer, and until recently, I was only using the receiver for a bike rack. I didn't have confidence in the install, what with the shabby ground (mentioned previously) and I had to add and change some fuses (prior to experiencing the issue). To the point, it was worth the cost of a new harness vs. my time and now have a harness that works (checked with meter and verified by the trailer). 75194

Reply from Jon G.

@A.R.M Glad to hear that you got it up and working! 75213

Steve S.

4 way plug. Issues. Only left rear trailer light works. DON'T GET IT. 99185

Reply from Jon G.

Start off by checking all of your light connections and grounds, as well as any fuses related to trailer towing on your tow vehicle. You also need to test the connector on your tow vehicle to make sure that it is actually sending out power on those circuits. 73760

Reply from Laura

@SteveS hey mine too.. it must be a strike or conspiracy going on with the right turn signals.. def can’t be us. In addition my left side stays on all the time, with or without the car being on.. . have to disconnect the wiring to the trailer to turn the trailer lights off .. ik my ground needs some tlc but that can’t be causing all the problems.. gonna find this inline fuse the instructions keeps mentioning.. 75821

Reply from Jon G.

@Laura I'd definitely make sure to check your ground as well - it can cause more problems than you think when it comes to wiring. 75827

Oscar S.

I have Nissan 04 4x4 with tow package My right side works but left does not I tried checking all fuses and even took some relays to see if any is connected to the right side but couldn’t figure it out?? Is there a fuse for left and another for right ? I check everything without a trailer used a special tool from camping world ?? Could I just jumper from my left light? 98909

Reply from Jon G.

What make is your 2004 Nissan, and are you talking about your trailer connector or the actual lights for your vehicle? Typically there are different fuses for the left and right stop/turn signals and jumping one wire to the other side would mean that all of those lights would work in tandem - including your turn signals. So that's definitely not an option. 73616

Jason B.

I tested the truck lights and all is good. I then did a test on the trailer plug and noticed that the brown wire which turns to a green wire seems to run to every light which make sense on it being running lights. My question is this should not have a short correct? If i actually hook up the brown wire i get the hazard lights to come on and the one signal light works. The running lights do not work. Any suggestions on where to look next. 98631

Reply from Jon G.

Are you testing for function according to the diagram in method 1 or are you strictly going by wire color? Make sure you are checking your wires by function and that you look at all of your wiring and grounds for your trailer since that's the problem side (see attached article). Look for any parts of your wires that might be bent or damaged and make sure your grounds are securely connected to a clean, bare-metal surface. 73436

Reply from Oscar S.

@JonG The problem is at the bumper connection, I also checked the connector to the connector 73626

Reply from Jon G.

@OscarS Cool, what is the make of your vehicle (2004 Nissan Xterra for example)? If your fuses look good and you aren't getting that signal at your vehicle-side connector then you need to trace the wring and look for any places that it might be damaged. 73645

Reply from Oscar S.

@JonG Yeah I tried that, relays look good, I think I might just replace them too hard to test them What do you think as my last resort? 73659

Reply from Jon G.

@OscarS As a last resort you can bypass your OEM wiring by splicing in a 4-Way connection like the Tekonsha # 119179KIT and then adding our upgrade kit # ETBC7 for fully-functioning 4-Way and 7-Way connections. 73666


On my trailer I have two black wires and a red one on both sides. How do I connect them to the new tail lights that have a yellow and brown wire on the left and a green and brown on the right 98320

Reply from Jon G.

For your tail lights the yellow should be your left turn/stop, the green should be your right turn/stop, and both browns should be your running/tail lights. You'll need to test the black and red wires on your trailer because those aren't standard colors. Just match up the functions and you should be good to go! 73161


O bought a T-one conector for my CRV- 2016, the one e trailer recommend for my car. The lights on the car works perfectly, and even the tail lights on the trailer. But turning lights (both) don’t work on the trailer. I already check the fusiles and they are ok. What can be wrong ? 97817

Reply from Jon G.

Have you tried using a tester to make sure the functions on the T-One connector are working correctly? If the T-One is sending power to the connector properly then the problem is on the trailer. Another way to verify this is by connecting your trailer to a different tow vehicle. For this you are going to check your trailer connector for any debris or corrosion and clean out accordingly. After that move on to inspecting the wiring for the turn signals on your trailer as well as any grounds or connections made. 72918

Reply from Tab

I did All that, the trailer works in another car. There is current going into the black box but not coming out 72920

Reply from Jon G.

@Tab In that case the module (converter box) sounds like it's defective and the unit will need to be replaced. If it's still under warranty you'll want to pursue that route. 73171


2018 Dodge caravan new Install of converter. and wiring No right brake or directional light . Tested green wire at module and have no power. Any ideas. 97410

Reply from Jon G.

If there is no power on the output side of the module then you'll want to test on the other side of the module (the input side) to determine if there is power actually coming from your van. If you do see power on the input side then that means the module is bad and you need to replace your wiring harness. If you don't see power then that means you need to check the connection for that circuit to your van, as well as any fuse or relay that would be used for that circuit. 71502

Reply from I

@JonG Jon there is power on the positive side of the converter, sorry thing is I ordered another one from another vendor and have the same thing with the same product and am a lost as what to do. I did return this product to you . The ground was good, and I had power to left side directional and brake light with both products. 71506

Reply from Bob C.

i have power on input side of this module. fuse is good, the funny thing about all this is this is, this is the third one i have tried , two from e trailer and another from another supplier. all of them have same results. my directional and all lights work at vehicle . however nothing going to flat wire for trailer after all connetions are made. i had rep on line for half an hour this morning and he again told me to send it in for another module. what can i do? 72685

Reply from Jon G.

So you aren't getting power on the output side of the module at all? Did you run the 12V power wire to the positive post on your Dodge Grand Caravan battery? 72937

Reply from Jon G.

So you have signals going to the module but nothing coming out? Did you hook up the 12V power connection for the module? 72938

Reply from Bob

Yes I did, even had a tech from hopkins condemned his module. I had two from etrailer and one from hopkins. I had power to left side but nothing going into or out on green wire. 72957

Reply from Jon G.

@BobC I saw that we shipped out a replacement to you. Is that one working or have you had a chance to install it yet? 73175


I have a boat Trailer hat has all lights work but stoplights I checked all the bulbs check the connections I still don’t understand can you help me 96922

Reply from Jon G.

For trailer wiring your stop and turn signals should be on the same circuits. The only time that your stop lights won't work while your turn signals still work is if your tow vehicle has separate lighting and your trailer connector on the vehicle is connected to a converter box that combines those signals. If this is the case you'll want to test the wire that carries the stop signal prior to it getting to the converter box. If you don't see anything then that means you need to check any fuses relates to this as well as the wire itself. If you do get a stop signal then you need to check the stop/turn wires on the output side of the converter (replace the converter box/wiring if you don't see anything). If you see signal then you need to check all of your wiring and connections past that, although I'm not sure how the stop signal would get separated from the turn signals past the converter. 71501


Installed new lights on pop up camper and new wire harness have all functions but when I step on brakes with right or left turn signal on the turn signals flash on the wrong side.and when I turn headlights on turn signals work fine but have no brake lights headlights off turn signals work fine until I step on brake then they are reversed help please. Have ground wires on lights and to frame shiny metel new plugs and wire too 95163

Reply from Chris R.

So the turn signals work correctly when you're NOT stepping on the brakes? That's pretty interesting (and odd). Have you tested the connector on the tow vehicle yet to make sure the issue isn't there? Test each pin while you run through the signals in the vehicle - see if you get appropriate power or if the turn signals jump to the other pin when stepping on the brakes. If the vehicle checks out fine then there has to be something going on with the wiring on the trailer - somewhere the circuits are touching each other (exposed wiring somewhere) or it's simply mis-wired before it reaches the tail lights. 70216

Reply from Tom L.

@ChrisR I'm having the EXACT same issues as Ray. Brand new harness/wiring, new lights. Everything is grounded properly to barn metal. Never had an issue with other trailers with my tow vehicle. I've rechecked the install four times now and its all properly hooked up. I'm baffled... 70460

Reply from Jon G.

@TomL The only other thing that I can think of aside from what Chris said is that your wiring circuits might be overloading. If you went from LED to incandescent lights or you added some lights to the trailer then that would pull more power and basically cause the circuits to spas out. Try disconnecting 1 light at a time to see if that reduces the load enough that everything is able to work correctly. 70573


Installing on a 2010 Toyota Venza. Followed instructions to a T. No lights work. Tested the trailer on a different vehicle and the trailer works. I replaced all the butt connectors and made sure the clips are secure and the ground is tight. Still nothing. Replaced ring on battery wire and still nothing. Did I get bum wiring?? 94401

Reply from Chris R.

Can you tell me what specific model harness you installed on the Venza? 69916

Reply from Laura

@ChrisR c56079 69934

Reply from Chris R.

@Laura Thanks for the info! If you're certain that all the connections are secure and the included fuse was also inserted and connected, it's definitely possible that the converter is bad. Are you able to test power on the wires going into the converter? If you show power there but nothing after, that's definitely what it is. Let us know if you purchased this harness from us if that's the case. 70215

Reply from Laura

@ChrisR I purchased the 4 prong tester and I am not getting any indication of power anywhere in the wiring, unfortunately. Replaced all connections earlier, and actually bought a new fuse just in case and installed that. I received this wiring from eTrailer with my hitch basket, yes. 70217

Reply from Jon G.

I will reach out to our Customer Service team and they will reach out to you in that case. 70572

John F.

Question: In 2013 I bought a 56183 module for my 2012 Jeep Liberty. After installed, output to running lights is live full time. Doubled & triple checked; everything seemed correct. Appears that module is routing the live feed to brown output wire. At that time, I clipped the brown and used the trailer only in daytime. Now, needing NYS inspection, I hooked it back up and called it DRL. Works fine, but need to unplug trailer to shut it off. Thoughts? 94314

Reply from Chris R.

It could just be a bad harness that needs to be replaced. I'm honestly not sure what else would cause constant power on the running lights circuit like that (assuming the tail lights on the Jeep itself are working correctly). I'm thinking the converter on the Curt # C56334 has an internal short. 69691

Reply from John F.

@ChrisR Thanks Chris. I thought internal short also. If it becomes a nuisance I'll replace the module. 69719

Dennis S.

I have a 2006 Chevy Avalanche. Can't get tail/marker lights to work on my boat trailer. 5 way connector. Recently snaged trailer wiring harness and had to re connect some wires. I soldered them. Had brake lights and turn signals when wires were damaged but no tail. Still dont have tail lights. I have tested for continuity to ground on all trailer circuits and I have continuity. Where does the tail light power come through the connector from the vehicle ( 5 pin)? Please advise. 91744

Reply from Chris R.

The tail/running lights circuit pin is the second pin on the 5-Way (right next to the ground pin). I wonder if there's a blown fuse under the hood of your Avalanche. Does it have a factory tow package? If so, the owner's manual should tell you which fuse is tied to the trailer running lights circuit - check its location and replace it to see if the issue resolves. 68346

Ryan M.

I rewired my trailer completely. New wires, lights and connectors. Nothing worked at all. After several test I connected the ground to the tail light/brake light and now I have blinkers and brake but not tail lights. Currently the ground is attached From the connector to the frame And to the brown wire. Does that sound right??? 86434

Reply from Chris R.

I'm a little confused. The brown wire is likely your running lights circuit - are you saying you have the ground wire connected to it? 68345

Daniel W.

I am going crazy. I have a jeep liberty 2009 and a toyota sienna 2005. Trailer lights work completly with the Jeep, but right turn and right brake light don't work with the toyota. (They work on the Van itself, so no blown fuse) Here is the thing though when I hook up one of those little testers to the toyota side trailer plug it tells me everything is fine!?! I am lost. Anybody an idea what is going on? 86140

Reply from Chris R.

That IS quite strange. A couple of things you can look at to at least get the troubleshooting process started. Inspect the connector on both your Sienna and the trailer. Look for any corrosion or debris inside the pins that may be preventing a solid attachment between the two, cleaning out as needed. Make extra sure the main harness ground wire on the Sienna AND the trailer is still securely attached to a clean, bare piece of metal. Weak grounds can cause all kinds of fun things to happen. Let me know what you find and we can go from there. 67966

Reply from Daniel W.

@ChrisR Ground is clean. Wire harness of trailer is new and harness of van most likely got never used before, therefor the plug is super clean too. I checked for wire that is rubbed through or broken. The only thing I can think of now is the converter box is toast and sends out a wird signal to the green wire. But since there is a signal the tester might think everything is fine. Could that be? I thought maybe the trailer wireing harness of the van can not handle that many clearance lights but the jeep can. so I took out the lightbulbs, but i still had the same problem. I have a multimeter, could that help me? 68111

Reply from Chris R.

@DanielW Yes, you could try using a circuit tester to see if there's an issue with the converter onyour Sienna. Test the wiring before the converter and after - see if you lose any power in between. 68344

Reply from Paulj

@ChrisR Check and see if you have different fuses for you for your trailer lights on the Sienna. I have a Nissan Frontier and I had a similar problem. Turns out that there are fuses for each signal light. Not sure why only one brake light is affected my running lights were fine but the brake lights and signal lights didn’t work. 69570

Bruce S.

I have a 1980 boat trailer and replaced all the original rear lights and side markers with LED's. I used crimp connections with shrink tubing over them, plus a liquid plastic sealer over that. Everything worked fine for a while, then the passenger side quit working. However, after I've backed the trailer into the water, the passenger side works again, as does everything else. I think there may be a short in the trailer wiring somewhere, does that sound correct? If so, would it be best to rewire the whole trailer, or start looking for a short on the passenger side? 85885

Reply from Chris R.

A short definitely sounds likely here. If the wiring isn't too difficult to access, I would just try inspecting the passenger side for any exposed or pinched areas that could be shorting out to the frame or a nearby wire. You should also inspect the trailer connector for any debris or corrosion that may be built up inside the pins, cleaning out as needed - rust in the connector can lead to a short as well. 67965

Dan C.

On a boat trailer, right turn signal works left turn signal on boat trailer and vise versa, changed wires once on trailer to match car, worked once, back to opposite, changed wiring again on trailer to match the car and it worked once and now it is back to opposite again. Any ideas for why it would keep changing? 84443

Reply from Chris R.

That's pretty strange. There has to be some exposed wiring on one of those circuits that's touching the other somewhere along the trailer - bridging those circuits. You can also inspect the trailer connector itself for any corrosion that might be built up inside the pins, cleaning out as needed. Sometimes rust can bridge two circuits together. 67419


Hi! i recently installed a 4 pin harness on my 2017 jeep cherokee. It worked perfect the first trip with it. this last trip, as soon as i plugged in the trailer, the trailer lights come on (with vehicle off and lights off). No other other functions work when the vehicle is on (turn signals/brakes), just the running lights remaining on. Any help would be great, thank you for your time! 81775

Reply from Chris R.

I might start by testing the 4-Way on the Jeep without the trailer hooked up. See if you're getting that constant power on the running lights pin. If not - then the issue is actually on the trailer side. I would start by making sure all your ground wires (both on the Jeep and trailer) are still securely attached to clean, bare metal. Inspect the pins on the trailer's 4-Way for any debris or corrosion that may be built up inside, cleaning out as needed. Let me know what you find and we'll go from there. 67113


Hi there, I have installed a Tekonsha 119191 (HD PLUS) in my Kona electric (2019). Everything went fine with the initial install. Tested it with probe circuit testers for correct wires. We hooked up a brand new Stirling/Marathon trailer and tested all functions. All blinkers, brake and running lights functioned (turned on and off) correctly. Problem 1: But then we realized that the right turn light on the trailer was not blinking. Left turn still blinked correctly. The Stirling trailer has combined brake/blinker lights so the light. Problem 2: Now, trailer brake lights are on even when the car is turned off. Car is a 3-wire setup with separate brake, tail, left and right wires. Subsequent testing with a multi-meter shows the 4pin plug at vehicle (without trailer) is putting out 14V on both the right and left signal wires all the time. Troubleshooting: Tested/Cleaned, Ground. Appears good. Reset power converter by removing fuse before 12V battery for 30 minutes. Running light (tested at 4PIN connector) is normal. 0V when lights off, 14V when running lights on. Left and right turn signal show voltage going up and down between about 14.2-14.8V when signal activated. Any hints greatly appreciated. 81632

Reply from Chris R.

Have you tested the converter to make sure it hasn't gone bad (unlikely but possible with a new harness). I would at least start there - test for power on the wiring going to the converter and then on the wires after the converter. If the constant voltage only starts after, then it's a bad converter and it'll need to be replaced. 67112

Reply from Chris A.

@ChrisR Hi Chris, No voltage coming through any of the vehicle side wires before the power converter so definitely bad power converter. If you could recommend a replacement I would appreciate it. 67249

Reply from Chris R.

@ChrisA Just to be clear, you don't show any voltage BEFORE the converter? If that's the case, then the converter actually isn't the issue (it isn't even being used at this point). Make sure you have the harness's power lead securely attached to the battery and that all your wiring is correct. For some reason the harness isn't even getting power from the vehicle. 67418

Jacques R.

I have a 2015 grand caravan I have had a trailer hookup on it since new all ways good haven’t used it in about 3 years found the four pin plug full of corrosion so I spliced a new plug into it only thing that works properly are the four way flashers did some troubleshooting connected a volt meter on to the the van’s four pin connector and found that I have voltage at the pins even when the van is completely off no key no nothing. also when connected to the trailer lights stay on all the time could the corrosion have caused damage in the converter. Any help would be appreciated 80901

Reply from Chris R.

The corrosion could have shorted out the converter. You can test this by testing for power on the wiring going TO the converter and then on the wiring after the converter to see if the constant power only shows after it. If so, the converter will need to be replaced. 66602

Greg N.

When I was driving from work my trailer wire came out when I hit a speed bump and it dragged the whole way home. I replaced the trailer end wire and everything worked. After a couple days later the tail lights stopped working on the trailer but brake light, turn signals all worked. Today I replaced the wire again and same thing tailights not working but everything else is. What is the issue here? 79238

Reply from Chris R.

I would try and inspect the running lights circuit wire on the trailer as far back as you can (towards the tail lights) to see if you can find any damaged or pinched sections that need to be replaced/repaired. You might also check the tow vehicle side by testing the running lights pin on the connector to make sure you get power - if not, the issue is somewhere on the truck. The most likely culprit would be a blown fuse under the hood. Let me know what you find and we can go from there. 64052

Bruce S.

I installed a new trailer wiring harness. The only way the lights will work is if I extend the ground wire to one of the rear lights. Is this alright? 78962

Reply from Chris R.

Absolutely. I wonder if you have an aluminum frame on the trailer, which just isn't the best surface to attach a ground. In these cases (or for any other reason that you just can't get a good ground on the trailer frame) running a wire all the way up to the main harness is a perfect solution. 63828

Bobby S.

I just put new lights on my trailer every thing works but when I turn on the headlights the right turn signal does not work .. can you give me any ideas as to why????? THANKS 78679

Tatiana S.

I needed to move my trailer lights off the main frame, and high up to be seen better, but now they need to be re-grounded. How is the best way to do that? Thank you. 77675

Reply from Chris R.

If there's still a clean portion of bare metal near where you're re-installing the lights, you'll just attach their ground wires there instead. Otherwise you'll just need to splice some longer wiring to the assembly's existing ground wire so you can reach bare metal for attachment. 63085

Reply from Christopher

@ChrisR What about an aluminum trailer? Assume I can't just ground it right to the frame? 63141

Reply from Chris R.

@Christopher Great question. You're right that aluminum isn't the best source for a ground attachment. In this case you'll want to run a separate ground wire from the assembly up to the main trailer harness ground. 63142

Ronnie T.

Hey I have two trailers and both of them when u turn off the truck the left side trailer light stays on dimly it doesn't do it all the time but more often than not it didn't do it until recently I have been pulling both for several yrs. 77476

Reply from Chris R.

I'm assuming the trailers are still hooked up to the truck (after turning the truck off). If this is the case, then there's likely a short somewhere on that left side tail light circuit. Try inspecting the truck's trailer connector for any debris or corrosion that might be built up inside/around the pins, cleaning out as needed. Sometimes corrosion can bridge a couple circuits together and cause a short like this. Let me know what you find and we can keep troubleshooting if needed. 63084


2 years ago had 4 wire harness installed by Chrysler on mini van. Worked great on utility trailer til now. Right brake light on trailer is on even when van not running. Or brakes on or blinker on. Put meter on wiring harness on van. Green wire shows 12v. Used white wire on harness as ground. Brown and yellow no power. Is this bad module? Or? Thx. 76157

Reply from Chris R.

If you're showing constant 12V power on the green wire (which is for right stop/turn) then it does indicate a bad harness module. You might first check to see if you notice any visually damaged wiring (exposed, frayed, pinched, etc) behind the 4-Way that needs to be repaired/replaced. Also inspect the connector itself for any corrosion or debris that might be built up inside the pins, cleaning out as needed. Otherwise to verify it's bad module, you could use your tester to test the wiring just before the module box and just after - if power is correct before the box then you know it's bad and needs to be replaced. 62208

Ron E.

This is great information. I have a 2017 Frontier and was given a boat and trailer and the brand new trailer light kit is dummy proof if you will. Have matched all the color coded connections and there is power according to my volt meter in the truck to the round adapter. When I plug the 4 prong into my adapter-nothing, no blinker, running or brake lights. I am very frustrated and have seen many suggestions that it is is the ground. I have drilled a new hole and used a new screw. Could my foreign truck have a different configuration for the wiring? I am at the stage of snipping the 4 prong, buying another that I can wire myself? 75638

Reply from Chris R.

What type of adapter are you using on the Frontier? 61759

Clark B.

The wiring harness on the trailer dragged on the ground and burned off one of the connector pins. I snipped off the connector, then noticed that two brown wires came together behind the trailer plug. The new plug just has one brown wire. I tried twisting the two brown trailer wires together and then with the brown wire on the new plug. Is that right? Otherwise I have green to green, yellow to yellow, white to white. My issue is the car brake and turn does not work on the left side driver side of the trailer. The yellow wire connection seems right. The left tail light does light when I turn the car lights one. 75605

Reply from Chris R.

I'm assuming your trailer uses a wishbone style harness, which has a separate running lights wire (brown) for each side of the trailer. Going by traditional trailer wire color/function, it seems like you installed the new connector correctly. The running lights also appear to be working, so the issue isn't with those two brown wires you combined. Make sure the left stop/turn circuit wire (yellow) is securely connected and that the main harness ground is still attached. You might also test the left side turn/brake circuit pin on the tow vehicle's connector with that function activated just to be sure you're even getting power from the vehicle. 61758

John H.

Hello,I just recently installed a hitch and wiring kit. I tested everything with a 12vlt tester and the trailer itself, everything worked fine. Now every time I use it it blows the 15amp fuse. With or with out the trailer I purchased a new 4 plug tester to further test once our spring snow in Chicago goes away. Question is , have you had issues with 2019 Jeep Limited X installs?If so it may point me in the right direction. I’m still going to trace and test the system for any shorts.Thank you 73443

Reply from Chris R.

Do you know which fuse in particular is blowing (what circuit it's connected to)? Usually something like this is the symptom of a short somewhere on the wiring. Inspect the connector on the trailer for any corrosion that might be bridging a couple pins together and take a look at any wiring you can access to make sure there aren't any exposed sections that could be hitting bare metal. I haven't seen in any specific issues like this with the 2019 Jeep models. Let me know what you find and we'll go from there. 59936

Curt G.

I have installed new led lights to my trailer. Everything works except my passenger side running light on rear led, but my marker/running lights on the passenger side work fine. Any suggestions? 73269

Reply from Chris R.

Since it's isolated to just that rear passenger side light, the issue is either with the light assembly itself or with the wiring between it and where it ties into the side marker light on the trailer. A good place to start is to make sure the light assembly is securely grounded to clean, bare metal - whether it does this though a dedicated wire or its mounting hardware. If it's good, I would next test for power on the wire right before the light (when hooked up to the tow vehicle and the running lights are on). If you don't get power, trace this wire up the trailer until it goes to the side marker light, looking for any pinched or damaged sections that need to be replaced. Let me know what you find and we can go from there. 59830

Joseph W.

I have a 2008 Chevrolet Trailblazer with factory 7 pin trailer light connection. I kust upgraded the trailer lights to a 5 pin system so i bought a 7 to 5 adapter all lights work on another vehicle but on Trailblazer on the right side i only get tail light no brake or turn signal. Could my problem be corrosion in factory outlet? 73237

Reply from Chris R.

Corrosion inside the factory 7-Way connector could definitely cause this, although it would have been a problem before too (if you had been using the 7-Way previously, without the adapter). Either way, it certainly wouldn't hurt to just visually inspect the connector and clean it out if needed. Let me know what you find and we can go from there if the issue isn't resolved. 59832

Reply from Joseph W.

Thank you, Chris R. Ill be looking into it further. 59842

Reply from Chris R.

Sounds good. Please don't hesitate to reach back out if the issue persists. 59880

Janis K.

I paid over 300.00 a year ago to have my trailer lights working again. One year later, the brake lights worked and the left signal light. I took it to one place recently and they told me the problem is with my car. Who do you suggest I go to to find out whats wrong. Just yesterday, I tested the lights, nothing came on. They wanted to charge me 90.00 an hour. I am 72 years old, know nothing about mechanics, etc. 72067

Reply from Chris R.

I don't have any specific recommendations as to where to take the trailer/vehicle other than to a local mechanic, but I can help troubleshoot the problem if you're up to trying (or have a buddy with some tools who can lend a hand). I'd start by testing the connector on your car - using a circuit tester to test each pin while the corresponding light function is powered. This lets you quickly see where the issue is. If you get power at all the appropriate circuits, you know the problem is on the trailer. If you don't show power then the issue is somewhere on the vehicle. If you let me know what you find we can go from there. 59048

Dean B.

Chris,I moved the ground wire to a different location, and it fixed it!Thanks for your help!Dean 72008

Reply from Chris R.

That's great news! 59028

Louie E.

I just rewired my trailer brand new harness and lights everything works turn signals stop etc the problem is when I turn on my lights in the truck everything stops working no running lights no turn signal no stoplight everything ! I turn the lights off and everything works again, any idea of what the issue is? The trailer lights ground off the mounting points I make sure the area was clean to create good ground i also grounded the white wire from the connector i screw it to the frame of the trailer, I tested the lights without hitching the trailer to the truck would that be the problem? do i need to hitch the trailer for the lights to work? I only plugged the trailer to the truck 71967

Reply from Chris R.

You shouldn't need to actually hitch up the trailer for proper light operation (if you did need to, that would actually indicate a weak ground somewhere). With that being said, this does still sound like the symptoms of a bad ground connection. Is your trailer by chance aluminum? What kind of tow vehicle do you have - is it equipped with a factory harness or is it something you installed afterward? I would try to check the ground on the tow vehicle harness as well. Also inspect the connector itself for any debris or corrosion built up inside the pins that needs to be cleaned out. 58960

Reply from Steve P.

I am having the same problem. I replaced both plugs however I was a little confused when rewiring boat side as i had 6 wires going into a 5 pin and wasnt sure where to put the extra wire. I have white,blue,green/brown,brown,yellow/brown, and yellow. The green/brown and brown split and go down the right side and the yellow/brown and yellow split and go down the left side.This happens just after the collapsible tongue.So all signals and brakes work but I have no running lights and side markers. Any ideas? 59933

Reply from Chris R.

It sounds like you have a wishbone harness on the trailer, but the wire colors used are bit odd. With this type of harness there's a running light wire for each side of the trailer (instead of just one that gets split right before it goes to the lights on each side). It would make sense that the green/brown is your right side running and the yellow/brown is your left side running - inspect these to make sure they're securely connected and in good condition. The fact that you have ANOTHER brown wire though is the strange part. Is this how you currently have those brown/yellow and brown/green wires run? 59938

Dean B.

I installed a trailer wiring kit, and when I hook up an inline LED indicator light, all the functions work lights, brakes and blinkers, but the trailer lights dont work when I hook it up to the trailer. Ive tried it on several trailers that I know the lights work, because we hooked other vehicles up to them. Could it be, that the ground is good enough to run the LED indicator lights, but not a good enough ground to run the trailer lights? 71904

Reply from Chris R.

That's definitely possible. The indicator wouldn't require much power at all to illuminate. You might try to use a multimeter so you can see the actual voltage you're getting on those circuits. If you can tell me what vehicle you have, along with the model wiring kit you used, I can try and provide some troubleshooting steps that are a little more specific. 58900

Amanda S.

Hi!! We just bought a 2000 Bergen horse trailer. It has light issues. When i picked it up i was able to get all lights except on the rear passenger side. I changed the plug and found the majority of the wires were not attached. We were able to get the majority of the lights to work as they should just going off the plug, left signal right signal and tail/markers but there seems to be a short with the brake light wire. It sparks when we apply direct power to it. The connection in the box had melted so it definitely got hot. Where would be the best place to try and find where it is shorting out? 71563

Reply from Chris R.

You've definitely got a short on that brake light wire. Honestly the best thing to do will be to try and inspect this wire the entire length of the trailer, if possible. There's likely an exposed section that's hitting metal frame (or a nearby wire). If the wire is really well hidden and difficult to inspect, you may be better off just cutting it off and running a new one. 58569

Ed A.

Front car Hazard lights flash normal. Rear hazard light left & right signal is going into converter but not out. Converter is combining turn signal and brake 5wire to 4wire or 3wire to 2wire depending on your terminology Rear lights have been removed from car and replaced with combination turn signal/stop LED lights. Rear hazard flasher will flash when brake is applied. 70659

Reply from Chris R.

Can you tell me exactly do you have the Beetle wired up with regards to the converter. How many wires are going into the converter (along with their functions)? 57634

Ed A.

Ive tapped in a 5 wire to 4 wire converter on a 2005 VW Beetle. All tail light functions work except hazard flasher. Power tested positive to converter. Hazard flasher works when brake is applied. Have replace converter once already. What next? Im stumped. 70546

Reply from Chris R.

Are the hazard lights not flashing at all, or is it just that the brake lights are flashing instead (where normally it would be the amber lights). A standard converter doesn't really have the "brains" required to decipher the difference between the hazards and brake lights, so it's going to send the circuit to the brake lights instead. With the converter installed, your brake lights will flash with the hazard lights on. This is completely normal and there's not really a good fix to resolve it. If this isn't what is happening though, please let me know and we'll go from there. 57567

Norm E.

Havent gt a converter yet, but testing my new five wire trailer lights LED, hooking the two lights together, grounding them on battery terminal, then testing each function seperately,each one works properly. Except green wire RT lights uptail light as does the red wire.Will a converter correct this or do I need to attach green wireto the four wire harness on the car, behind the female connector? Very confused.BTW-lights are not yet on trailer, so Im just testing them ona battery before I install them.Thanks much for your time. 70268

Reply from Chris R.

If I understand correctly you are simply testing your new trailer lights by connecting each wire directly to power. Is that right? If so, I'm not sure what would cause the lights to malfunction other than an issue with their wiring or the light itself. A converter wouldn't be needed (at least not yet). Please let me know if I am misunderstanding something or if you can provide a bit more insight as to your current lighting setup, along with the model number of your new assemblies, and I can definitely look into this further. 57300



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