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Expert Answers about Wiring


  • Troubleshooting Trailer Wiring When Running Lights Do Not Work
  • It sounds like there is a ground wire issue on your trailer. Since you said you checked the vehicle harness and it checks out we can rule that out as the issue. You will want to use a circuit tester like part # 3808 and check the wires coming out of the trailer connector when plugged into the vehicle. Make sure the pin for the ground on the trailer connector is not corroded or bent. Check the lights and make sure the ground wires are securely fastened to a clean bare metal surface, and...
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  • Troubleshooting 12 Volt Accessory Circuit Not Functioning After 6-Way Connector Install
  • It is possible that you shorted out the 12 volt trailer wiring circuit of your truck while you were wiring in the connector. Since this circuit would have voltage all the time it would be pretty easy to short it out while wiring up a new connector. Check the fuse box for the 12 volt accessory trailer circuit relay/fuse and replace as needed.
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  • Troubleshooting a Vehicle that Trailer Wiring Stopped Working After Installing LED Taillights
  • The converter box of your wiring harness is looking for the amount of amperage on the circuits that is associated with incandescent bulbs. Since you switch to LEDs that draw considerably less the trailer wiring isn't functioning. You can either go back to your incandescent bulbs to fix the problem or you can install a different taillight harness like part # 119190KIT that is designed to work with LED taillights.
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  • Troubleshooting Trailer Running Lights Not Working on a Trailer
  • First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # 3808 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue. Make sure that the trailer side connector are clean...
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  • 7-Way Trailer Connector 12 Volt Circuit has Power All the Time
  • The 12 volt circuit on a 7-Way that was hardwired into a vehicle is going to have power all the time. Provided nothing is plugged into the 7-Way that draws power from the 12 volt circuit then it would not be a problem. The little LED light would take months to drain a vehicle battery if you were to let it sit all that time and never start the vehicle. But there is a way that you can shut off power to the 12 volt circuit when the vehicle is off. You would need battery isolation solenoid...
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  • Troubleshooting Trailer Lights That Go Off When 2011 Dodge Ram Is Put in Reverse
  • It sounds like the wiring on your trailer 7-way connector is wired incorrectly. Try using a circuit tester like part # 3808 and testing each pin on the trailer connector for function. If the pins on the connector are compared to the hands of the clock, the pin at the 1:00 position is the 12-volt accessory feed. This pin should show constant voltage. The pin in the 3:00 position should show voltage when the right turn signal and brake is activated. The pin in the 5:00 position carries the...
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  • Troubleshooting 2003 Chevy Tahoe that 7-Way Stopped Functioning
  • If the trailer wiring fuses of your 2003 Chevy Tahoe are good and the 7-way still isn't working properly the problem is either that there is corrosion on the 7-way that would need to be cleaned off with fine grit sandpaper or the wiring to the connector itself is damaged somewhere between the connector and the vehicle fuse block. Check out the connector, most likely you will either find damaged wires behind the connector or corrosion that needs to be fixed or there is corrosion on the...
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  • Troubleshooting Trailer Running Lights Not Functioning After Boat Launch
  • Water and electricity don't mix well so I would imagine the issue you are having with the running lights of your trailer are related to your trailer being submerged in water when you launched your boat. First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # 3808 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. I suspect a blown fuse on the tow vehicle is to blame...
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  • Troubleshooting 7-Way Trailer Connector on 2003 Chevy Tahoe
  • Check that the harness that plugs into the rear of the trailer connector is pushed in all the way. I'd recommend using a circuit tester like part # 40376 on the wiring behind the trailer connector. If you're getting power on the harness but not on the trailer connector, the connector is faulty, damaged or corroded and would need to be replaced with a new connector such as part # HM40975. If you don't see any power on the harness, you'll need to check the fuse box under the hood. The...
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  • Trailer Brakes Activate Every Time Turn Signal is Used
  • It sounds like you wired the brakes into the combined stop/turn signal circuit on the trailer. Trailers use what is called a combined system meaning that the brake lights and turn signals are on the same tire. So when you are using the turn signal the wire is energized and will apply the trailer brakes when the light blinks. To use the electrical trailer brakes you have to have a dedicated wire just for the brakes and you must use a brake controller in the tow vehicle. The most common...
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  • Recommended Trailer Wiring Harness for 1998 Holiday Rambler
  • Your 1998 Holiday Rambler shouldn't require a special converter but if the installation was completed per the instructions and this is the second unpowered converter that you have tried, I recommend trying a powered converter with circuit protection like the Tow Ready, # 119190KIT. With a powered converter the power is drawn directly from the vehicle's battery which virtually eliminates any draw on the taillight circuit.
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  • Troubleshooting Brakes of Logan 3 Horse Trailer Towed by 2015 Silverado 3500 w/ OEM Brake Controller
  • Good thinking testing the truck with your other trailer, you've ruled out the truck as being the cause of the problem. Since all the trailer lights are functioning on the trailer, the problem is likely in the braking system. Start with the trailer plug, and closely examine it for damage or corrosion. If it's damaged or corroded, you can replace it with a connector like part # H20044 for a 6 foot long wire or # H20046 for an 8 foot long wire. Trace the brake output circuit back to...
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  • Troubleshooting Trailer Brakes that Dont Apply
  • I am glad you were able to figure out the issue with the circuits being swapped. That is a pretty common issue with the 6-way wiring setups. Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # 3808, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake...
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  • Troubleshooting a Blown Fuse Every Time a Trailer is Connected
  • If your taillights keep blowing every time you connect your trailer, it seems to me you have a short in the running light on your trailer. I recommend starting at the trailer connector and check for any corrosion or damaged pins. If there is corrosion, remove the wires from the connector as it could have spread inside the connector. Also, check the vehicle side connector for any corrosion or damaged pins. Fix as needed. If the connectors are clean, follow the running light wire looking...
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  • Troubleshooting Dim Trailer Running Lights
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare...
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  • All Trailer Lights Flash When Using Turn Signals and Running Lights
  • There could be a few potential problems here. Since the lights work as they should until the running lights come on, then the issue is most likely on the trailer. Problems like this are typically associated to a poor ground connection. To make sure the problem is isolated to the trailer, I recommend using a simple light tester, like part # 40376, to test the trailer connector on your tow vehicle to make sure it is functioning properly. I have attached a video that shows how to do this....
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  • Troubleshooting Low Taillight Circuit on Trailer Taillight Converter
  • What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the # 3808 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test the output side of the box to see if the current is making it through the converter. If not then the problem is that the converter box has shorted itself out and would need to be replaced. Before you replace it you will want to inspect the...
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  • Which Fuse Provides 12-Volts to 7-Way Connector on 2009 Chevy Silverado 3500 Diesel
  • If the 12-volt pin on your trailer connector isn't working, you've got a missing or blown fuse or the wiring connection at the fuse box under the hood wasn't finalized. You're looking for a 40 amp fuse, located in position # 68 in the fuse box under the hood. The fuse protects one of the nearby power studs on the side of the fuse box, which is where the wire that provides power to the 7-way should be connected. If it's not, you can find the wire bundled up under the master cylinder...
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  • Troubleshooting Humming Brakes when Hazard Lights Flashing On 1996 Chevy C1500
  • A pulse preventer, part # 5501, should stop this problem. The flashers are sending feedback into the brake controller and pulsing it. Find the spot where the brake controller is spliced into the wire from the cold side of the stoplight switch. This is typically the red wire on the brake controller. Then just past this (away from brake controller) cut the vehicle stoplight wire and install the Pulse Preventer inline with the yellow wire on the side that the stoplight switch and brake...
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  • Troubleshooting Weak Trailer Brakes on a Toy Hauler Even After New Axles
  • This could be a magnet wiring problem. It is unlikely that the magnets are bad on new assemblies, but if the wiring is not properly connected, it could cause problems. Check to see that the magnets are properly grounded to a clean, bare metal surface free of corrosion. A bad ground would not allow the circuit to be complete and lead to the brakes not performing like they should. You can also try running all of the brake grounds back to the main ground of the trailer. The new brake assemblies...
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  • Troubleshooting Trailer Running Lights that Aren't Working
  • The first step to troubleshoot your problem would be to determine if the wiring problem exists with the vehicle or the trailer. Turn on the vehicle headlights, and use a circuit tester like part # 3808 on the pin on the trailer connector that feeds the running light circuit. If your vehicle has a 4-pole connector, test the pin being fed by the brown wire. If you are dealing with a 7-way connector, you would test the pin in the 11:00 position. If the tester indicates voltage on the pin...
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  • Why Do the Brakes of My Gooseneck Trailer Lock Up When 6-Way Adapter is Connected
  • The problem you are experiencing is due to the fact that there are two different ways 6-way trailer connectors are wired. The only difference between the two is that the brake output circuit and the 12 volt power circuit are swapped. So basically what is happening is that the 12 volt power circuit of your truck is sending voltage to the brake output circuit of your trailer which is locking them up. What you need to do is swap the wire going to the center pin of the 6-way adapter with...
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  • Right Turn Signal on a 2006 Chevy Silverado Isn't Working Properly
  • First thing I would do is disconnect the trailer from your 2006 Chevy Silverado so you can check the vehicle side connector with a circuit tester like # 3808. Test the right turn/brake signal and if it's still not working there might be a blown fuse or relay. Make sure the connector is clean and free of any dirt or corrosion. Using a wire brush should suffice. If the wires behind the connector are frayed, cut them off at the damaged area and re-splice back into the wiring. Another...
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  • Troubleshooting Electric Brakes Not Working on Dual Axle Box Trailer
  • In order to determine why the brakes aren't working on your dual axle trailer, I recommend first cutting the blue wire 5-6 inches behind the controller and use a circuit tester like the Quickee, # 3808, to verify that power is present. Power should be present when the manual override control is used. If no power is present, the brake controller may be malfunctioning and require replacement. The next step would be to test the 7-way on your tow vehicle. Using a circuit tester, verify that...
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  • Troubleshooting Trailer and Truck Lighting Problems When Trailer 7-Way is Connected
  • Thank you for providing a thorough description of the truck and trailer lighting issues you're having. The various problems you describe COULD be related to the same issue, corrosion in the trailer connectors, but there may also be multiple things you'll need to attend to. The best way to troubleshoot your concerns is to unplug the trailer from the truck's 7-way and then to test each one individually. Since your RV is used, it's wiring is my prime suspect. Step one for troubleshooting...
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  • Troubleshooting Fuse Blowing in 2006 Chevrolet Silverado After New 7-Way is Installed
  • From the details that you have given it is pretty apparent that the issue is with the 7-way on the 2006 Chevrolet Silverado 2500HD. I recommend reviewing the installation instructions and making sure that each step was completed and that nothing has come loose. I would also check to make sure that the ground is secured to a clean and corrosion free bare metal surface. I have attached a wiring article for you.
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  • Troubleshooting a Right Turn Signal on a 7-Way of a 2000 Ford F-150
  • First thing you should do at this point is test the 7-way of the wiring harness with a circuit tester part # 3808 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue. Make sure that the trailer side connector is clean...
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  • Troubleshooting Trailer Blinker that Stays Solid
  • First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # 3808 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue. Make sure that the trailer side connector are clean...
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  • Turn Signal On 2012 Kia Sorrento SX Hyperflashing After Installing Wiring Trailer Harness
  • Sounds like you are experiencing what is termed 'Hyperflashing'. My best recommendation is to remove the # C56146KIT and see if the problem still persists. If it does there is a problem in the vehicle wiring. If the problem goes away, then the converter is probably bad and the harness needs to be replaced. If you do find you need to replace it I recommend the Tow Ready Wiring, part # 119147KIT. We have had good success with our customers that have used this kit. Please keep...
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  • Trailer Light Fuse in 2004 Chevy Silverado Blows When Any Trailer is Connected to 7-way
  • Since you have the issue with your truck's trailer left turn fuse blowing no matter what trailer is connected, the issue is likely to be in the truck's 7-way socket or the wiring leading to it. Corrosion can build up in the truck's 7-way socket - either on the pin contacts themselves or even inside the back of the connector - and this can cause two circuits, such as the trailer left turn/brake circuit and the 12V auxiliary trailer power circuit, to become bridged together. The round...
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  • Reading 12-Volts on 6-way Connector of Kaufman Tilt Bed Trailer
  • Do you mean that you're using a circuit tester on your 6-way connector on the trailer (not the truck) and you're reading 12 volts on one of the pins? The only way that would happen would be if you had a battery mounted on the trailer. Typically, the battery is connected to the 12-volt supply circuit off the 6-way to receive a maintenance charge.
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  • Troubleshooting Left Stop/Turn Light Not Functioning On Trailer
  • Sounds like you are trying to figure out why the left brake light on your trailer isn't functioning but the rest of the trailer lighting seems to be working. Typically this problem is due to a bad ground on the light assembly. The light grounds should be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt...
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  • Electric Trailer Brakes Make Noise But Will Not Engage
  • The first thing you will want to check is the output voltage on the brake controller. If it is set too low it will not send enough power back to engage the trailer brakes. For testing purposes it is easiest to set it to full power. Using a meter or circuit tester like # 40376 make sure that power is getting back to the trailer connector, which it does sound like it is. Then with the trailer connected make sure power is getting to the brake magnets which again it sounds like it is. That...
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  • Left Blinker Flashes Fast After Installing Trailer Wiring Harness on a 2014 Chevy Camaro
  • In order to determine the functions of the wires on your 2014 Chevy Camaro you will need to use the included circuit tester that came with # 119147KIT. What you are describing sounds like hyperflashing which can happen when using LED lights but usually not stock LED lights on a vehicle. If the issue is happening on a trailer then the hyperflashing is a result of not enough load on the system. Installing a load resistor such as # P230004A in line of the affected circuit would cause more...
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  • Troubleshooting Trailer that Right Turn Signal Comes On But Won't Blink
  • First you will want to check the right turn signal of the vehicle wiring connector to make determine where the problem is. It's either the tow vehicle or the trailer. You will want to use a circuit tester like part # 3808 to check the pin on your connector for intermittent voltage when the blinker is applied. If the voltage of the vehicle checks out like it should then I would suspect the problem is either that the light assembly isn't grounding properly or it is shorting out to the...
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  • Troubleshooting 4-Way Harness On 2013 Ford F-150 And Trailer Wiring
  • If you installed the 4-way connector at the back of your 2013 Ford F-150, you can check the connector first to make sure it is wired correctly. I recommend using a circuit tester like part # 3808 and check each pin for function. You want to make sure the pin connected to the yellow wire shows current for your left turn and brakes, green is for right turn and brakes, brown is for the tail lights, and the white wire is the ground which should be secured to a clean, bare metal surface. You...
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  • No 12 Volt Power to Trailer Connector on a 2002 Chevy Silverado
  • This is not an uncommon situation for your generation of Chevy Silverado. If you remove the cover on the power distribution box, look for a row of larger fuses on the left side of the box (if facing the motor from the front of the truck). If there is no fuse or a blown fuse in the slot closest to the front of the truck in that row then you will need to install a new 40 amp fuse. If there is no wire attached to the post nearest that fuse location you will have to manually run a wire from...
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  • Low Beam Headlight Not Working But High Beam Does Work
  • It sounds like there could be a fuse blown or damage or corrosion in the bulb socket. Bulbs that have both high and low beam functions have 2 filaments in them so it is also possible that the low beam filament has burned out. If you can tell me the year, make, and model of the vehicle I can recommend some replacement bulbs.
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  • Troubleshooting Brake Light/Left Turn Signal on a Trailer Towed by 1999 Chevrolet Silverado
  • The first thing I would test is the trailer connector on your 1999 Chevrolet Silverado using a circuit tester like part # 3808 to see if the problem lies in the trailer or in your vehicle. See the linked video to see how to do this. You will be testing for brake/stop light functionality of the circuit and this will tell you if the problem is on the truck or the trailer. Also to ensure that your trailer connector is wired properly, we recommend using the circuit tester to match pins by function....
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  • Brake Controller Does Not Work when Using 7-Pole Round to 7-Pole Blade Adapter
  • It does sound like something is mismatched in the wiring. Either the truck or the trailer would appear to not be following the standard pin out. On the output side of adapter # HM47425 the brake pin is in the 5 oclock position if looking at the pins. If looking at the back of it where the wires attach it would be in the 7 oclock position. I have included a link to a help article that shows how different trailer connectors are normally pinned out so you can compare them with what you...
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  • Brake Lights on 2012 Semi Trailer Work But Not Brake Lights on 2004 Freightliner
  • Since your semi trailer brake lights are working but the tractor's brake lights are not working, it sounds like the wiring for the trailer lighting is independent of the tractor's brake lights. If all of the trailer lights operate as they are supposed to then I would first check the fuse panel in the tractor for a blown brake light fuse or perhaps for corrosion in the fuse holder. You can also check the individual brake lights on the tractor for signs of a weak ground connection (especially...
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  • Blinkers Do Not Work with Running Lights On on a 2007 Freightliner XL Classic
  • You will first need to make sure that the new tail lights are wired the same as the old ones. There are basically 2 types of wiring systems. First there is a 2-wire system that has combined turn signals and brake lights on the same circuit/bulb. And there is a 3-wire system that has separate circuits/wires and bulbs for turn signals and brake lights. On many tail lights the functions of the wires is listed on the back of the assembly. Since there isn't a standard wire color/function code...
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  • Trailer Brake Lights and Turn Signals Work But Running Lights Do Not
  • In order to determine where the problem is you will first need to test the connector on your 2011 Chevy Silverado without the trailer plugged in. Basically you will use a circuit tester such as # 3808. Turn the running lights to the on position in the truck. Then test the connector to see if the running light circuit has power. If it does not then the issue is on the vehicle side. It could be a blown tow package fuse. Using the owners manual, find the location of the tow package fuses...
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  • Rental Trailer Lights Not Working with 2011 Mercedes ML350 and Prodigy RF Brake Controller
  • The Prodigy RF brake controller # 90250 is a sensitive unit. You will need to make sure you follow the hooking up procedures to the letter or it may not work properly. If you still have problems make sure that none of the tow package fuses on your 2011 Mercedes ML350 are blown. It is also possible that the trailer lights were the problem. I would assume the rental place would check that and not leave it up to you! If the trailer happened to have LED lights you would need a special...
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  • Troubleshooting Trailer Brakes that Lock Up After Rewiring Trailer
  • It sounds like the 12 volt circuit of the 7-way wiring is shorting out to the brake output circuit which is causing the brakes to lock up when the trailer is connected to the tow vehicle. This is most likely due to exposed wiring from when you rewired the trailer. I would go over all the connections you made looking for exposed wire and fix as necessary. I attached an FAQ article on trailer wiring for you to check out as well.
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  • Troubleshooting Trailer Taillight Converter Installed on 2006 Volkswagen GTI
  • When the turn signals are activated, and you get 'bleed over' into the other turn signal, it can indicate a poor ground connection. Check the ground connection on the trailer, where the white ground wire from the trailer connector connects to the trailer. This is usually found on the trailer tongue. Make sure the connection is secure, and not corroded. Check the grounding point for each lamp. Some lamps have a separate ground wire that connects to the trailer frame, others ground by the...
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  • Troubleshooting Dim Lights on Trailer and Some that Don't Turn On
  • It sounds like there is either a lot of corrosion on either the vehicle's trailer connector or the connector on the trailer. Or, your trailer has a ground problem. First thing you should try is thoroughly cleaning the pins of the connectors with fine grit sandpaper to get the pins down to bare metal. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces....
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  • Running Lights on Trailer Stay On All the Time
  • This sounds like a ground issue or it could also be a short. Look for any pinched or frayed wires on the trailer and fix as needed. This could cause a short resulting in constant power draw. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector...
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  • How Many Circuits are Supported by the Optronics 7 Pole to 5 Pole Flat Wired Adapter # A57WB
  • Thank you for your recent purchases from etrailer. The Optronics 7 Pole to 5 Pole Flat Wired Adapter # A57WB that you purchased is intended to allow a tow vehicle with an RV-style 7-way blade type trailer socket to connect to a trailer that uses a 5-pole flat type connector. The linked article on trailer wiring shows these and other connector types commonly in use. The 5th wire on a typical 5-pole trailer is usually blue in color and is there to carry signals for electric trailer...
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  • Troubleshooting Trailer Left Turn/Brake Light Not Functioning on Trailer Wiring
  • Most likely the problem is the ground of the trailer's left side turn signal and brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. To rule out your tow vehicle as the problem you can use a circuit tester like part # 3808 to test...
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  • Troubleshooting 7-way On 2004 Ford F150 Not Showing Left Turn Signal
  • If you've tested the 7-way on the vehicle, and have determined that you have no signal on the left turn signal pin, closely examine the trailer connector. Make sure it's not damaged or excessively corroded and clean/replace if necessary. If the trailer connector checks out okay, take a look at the wiring harness that feeds the 7-way, right behind the connector. Find the yellow wire in the harness and use a circuit tester like part # 40376 to test the wire as a helper activates the left...
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  • Troubleshooting Trailer Brake Lights that Don't Function With Headlights or Running Lights On
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare...
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  • Troubleshooting Dim, Pulsating Trailer Running Lights
  • It sounds like the problem is on the trailer wiring. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue,...
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  • Troubleshooting Trailer Lighting Where Only One Running Light Works
  • Since all of your trailer lights operate properly with the exception of one of the running lights, this tells us that the vehicle wiring harness is probably working properly. I would first carefully check the bad light's ground and power wires to ensure that both are secured. If the light uses a separate ground wire, usually a white wire like on # MCL36AB, that ground wire needs to be affixed to the trailer frame, to a clean rust-free bare metal surface. If the light is the type that...
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  • Troubleshooting Honda Ridgeline Blinkers that Stop Working when Brakes are Applied
  • Typically when this issue arises on a Honda Ridgeline the issue is that the "small lights" fuse under the hood is blown. This may or may not have been related to the trailer wiring you installed.
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  • Troubleshooting a Trailer that Taillights, Blinkers Both Flash and Only One Running Light
  • It sounds like the problem is the wiring of your truck like it sounds you have determined already. What I would do is use a circuit tester like part # 3808 to test the circuits of your 7-way while a buddy applies the different taillight functions. Use the diagram I attached to the right for more info. The problem could be as simple as corrosion on the connector that needs to be cleaned off (inside or outside of the connector), or it could be that the wires of the connector have shorted...
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  • Troubleshooting Inactive 7-way 12 Volt Accessory Circuit of 2007 GMC Sierra 1500
  • I am going to go out on limb and say that you are trying to activate the 12 volt accessory circuit on the 7-way of your 2007 GMC Sierra 1500 and it isn't working so you are looking for a fuse to replace? Actually what is happening on your truck is that there are a few underhood connections that need to be made in order for this circuit to be completely activated. For more info on this check out the FAQ article I attached to the right and scroll down to the section titled, "Finalizing...
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  • Troubleshooting Right Stop/Turn Circuit on Aluminum Trailer
  • It sounds like you have narrowed the problem down to being somewhere on the right stop/turn circuit (green wire) on the trailer. If you can use your circuit tester to test that circuit as close to the light assembly as possible to see if the light is getting voltage or not. The other possible problem is that the ground of the assembly isn't sufficient. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds...
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  • Troubleshooting Trailer Brakes that Lock Up When Connected to Trailer Wiring
  • This is a fairly common problem for trailer setups that use 6-way connectors like the # PK11604 that you referenced. The issue is that there is two accepted ways the connector can be wired up. The only difference between the two setup is that the brake output circuit and the 12 volt accessory circuits are swapped. It sounds like your vehicle is wired one way and the trailer is wired the other way. What you will need to do is swap the two circuits on either the trailer or the truck....
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  • Horse Trailer Brakes Lock Up When Connected to 1999 Ford F-250
  • It sounds like either the trailer side connector is not pinned to match the vehicle side connector or there is a short circuit (possibly due to corrosion on the pin or inside the trailer connectors) causing the brakes on the trailer to lock up. The easiest thing to check first is for dirt/corrosion on the pins and inside each of the trailer connectors. Then you can make sure that the trailer side connector is wired up to work properly with the vehicle side connector. I have included...
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  • Troubleshooting Non-Functioning Running Lights on Trailer Towed By 2014 Nissan Frontier
  • It sounds as if you might have a blown fuse. You'll need to check the diagram on the lid of the fuse box under the hood, and look for a fuse for the trailer running or parking light circuit, and replace it. Before plugging the trailer into the vehicle, you'll want to closely examine the running light circuit for any shorts that would have caused the fuses to blow. Start at the trailer connector, and examine it for damage. Trace the running light circuit (usually a brown wire) back to...
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  • Troubleshooting Trailer Left Turn Signal That's Not Working
  • Without knowing the year, make and model of the vehicle, I can't really provide any specifics but I can provide you some general things to check. The first thing you'll want to do is determine if the problem is in the vehicle or the trailer wiring. The easiest way to do this is to plug in another trailer if one's available and see if the problem persists. If this isn't possible, use a circuit tester like part # 40376 on the trailer connector on the tow vehicle. Activate the left turn...
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  • Does a Breakaway System Battery Affect Everyday Trailer Brake Performance
  • Electric trailer brakes can work on a trailer that doesn't have a breakaway system. So the answer to your question is no, the breakaway battery would not affect how normal trailer brakes will operate under normal circumstances. The only time the breakaway battery will change how the brakes are performing is when the pin of the system has been pulled and the voltage of the battery is being applied to the brake assemblies. I attached an FAQ on breakaway systems plus an FAQ on troubleshooting...
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  • Troubleshooting Install of Tow Ready Wiring Kit # 119179 Doesn't Work With Running Lights are On
  • The Trailer Wiring Kit part # 119179 fits several vehicles and several different configurations of vehicle wiring. Without knowing what vehicle you have or what style of taillights you have on your vehicle it would be hard for me to say for certain. Based on the description of how you installed the harness it sounds like you have it wired up like a 2 wire system. It could be possible that you have a 3 wire system and would need to wire it up like the illustration I attached.
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  • Troubleshooting Factory Trailer Wiring for 2003 Ford F250
  • First I recommend cleaning the connector and make sure there is no corrosion on the pins. Check the wires at the back of the plug. You may need to remove the wires from the connector as corrosion can build up in the connector. If all of the connection points are corrosion free, then begin testing the wires themselves. Since you are not receiving a signal on some of the pins I recommend tracing those wires back till you find a point where the signal is active. It may be that connection...
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  • Troubleshooting 4-Way Wire Harness installation On 2009 Cadillac SRX
  • The wiring harnesses and kit, part # HM48895 and part # HM46155 you referenced in your question are not designed to be a fit for your 2009 Cadillac SRX. If you find that you have the correct wire harness for your SRX you can check the wiring to make sure all of the wires have been connected as the instructions state. Also, you will want to make sure the ground wire has been secured to a clean bare metal surface. Loose or corroded grounds can cause some of the same problems you described....
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  • 2008 Chevrolet 2500HD 12 Volt Battery Wire for 7-Way Connector
  • Sounds like you have the correct 7 way connector and the correct pins, but you are missing the wire that runs from the power posts to the connector. First let's make sure. In the under hood accessory fuse block there are two power posts on the engine side of the block. The post closest to the front of the truck should have a wire connected to it that runs back to the factory trailer connector and provides 12 volt power at the 1:00 position as you have stated. If the wire is not already...
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  • How to Test the Trailer Light Functions of a Trailer with a 4-Way
  • There is, but I will warn you it's pretty expensive. The Hopkins Tow Doctor Trailer End Test Unit # HM50928 is designed to test the connector on a trailer for function and would be perfect for what you are trying to do. Check out the review video I attached. A much more inexpensive option would be to use a jumper wire from a car battery's positive post to put voltage on all of the pins of your trailer's connector. You would need to test the three male pins next to the female pin....
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  • Troubleshooting Trailer Wiring That all Blinks When Right Turn Signal is Applied
  • You are having some interesting wiring issues on your trailer. First thing I would recommend you do is check to make sure all of the wires are grounded properly. Ground issues can cause bizarre trailer wiring behavior. Each lamp should be grounded either by its mounting studs being in direct connection with the trailer frame or by each lamp's ground wire being connected to the trailer frame. Next, you will need to inspect the wiring from the connector to the light assemblies looking...
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  • Replacing 4-Pole Trailer Connector on Trailer With 7 Different Circuits Feeding It
  • It sounds like you've got a pretty good handle on what you're dealing with. You're correct, the green is right turn/brake, yellow is left turn/brake, black/green is right taillight and black/yellow is left taillight. The remaining wires are almost certainly grounds. I'm guessing you're not the original owner of the trailer or the person who wired it last time. Rather than grounding each trailer lamp directly to the trailer frame by its mounting studs or individual ground wires connected...
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  • Troubleshooting Trailer Wiring that Blinkers Dont Work When Headlights are On 2007 Toyota 4Runner
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare...
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  • Troubleshooting 7-Way Connector of 2006 Toyota Sequoia With No 12-Volt Feed at 7-Way
  • If your 7-way on your Sequoia was installed at the factory, the 12-volt circuit should be active. Check the fuse box under the hood for a blown or missing fuse. If there's no blown fuse, you trace the 12-volt circuit from the rear of the vehicle looking for a loose connection, but abandoning the original and installing your own circuit as described below might be the simplest course of action. If the 7-way was installed aftermarket, check the terminal for the 12-volt pin at the rear...
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  • Turn Signal Not Working when Using Brakes and Using Hopkins 40955 Wiring Kit
  • Since you have a new trailer connector on your vehicle that tells us that the issue is likely on the trailer somewhere and it sounds to me like it is a bad ground. Make sure all your ground connections are good and clean. There will be a ground connection coming from the trailer connector to somewhere on the trailer tongue and each of your trailer lights should have a ground connection through either a ground wire ran to the trailer frame or grounded through a mounting stud on the light...
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  • Troubleshooting a Trailer Right Brake Light Won't Function
  • It sounds like the problem is on the trailer and is ground related. I would inspect the grounds of the light assembly you have installed on the right side of your trailer and make sure it is connected to a clean metal surface. A lot of assemblies ground through their mounting hardware so you will want to make sure that the assemblies are connected to a clean metal surface. The brake lights will require a better ground than the blinker since it only illuminates one circuit for the blinker. I...
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  • Trailer Connector on 1994 Ford F-250 Only has 12 Volt Power on the Center Pin
  • If it is really a 6-Way and not a 7-Way blade style trailer connector then the center pin being hot would indicate that particular pin is the 12 volt power circuit. But the other functions not working could mean that tow package wiring fuses and/or relays are missing or need to be replaced. Check the truck owners manual to find the locations of any and all fuses related to the tow package wiring. If the wiring was added and is not factory then you will need to check the wiring connections...
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  • Trailer Brake and Tail Lights Go Out when Headlights on 2000 Chevy Silverado Come On
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare...
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  • Trailer Lights are Erratic After Switching to LED Lights
  • Jesus is a good driver, but not a trailer expert. And that's ok because your trailer is not possessed . . . well, it could be, but that is not what is causing this problem. What you have here is a ground problem. Ground problems can cause all sorts of funky things to happen. The good news is ground problems are usually very easy to fix. The bad news is that you have to find the problem before you can fix it. Ground problems normally show up when there is more draw on a system such as...
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  • LED Trailer Lamps Stay Illuminated When Tow Vehicle is Shut Off
  • When the tow vehicle is shut off, the only pin on its 7-way trailer connector that should show any power is the 12-volt accessory circuit, which is the pin in the 1:00 position. If the trailer lights are illuminating when the tow vehicle is shut off, the only possibility is that there's a small short either in the 7-way connector or in your adapter that is allowing some power from the 12-volt accessory circuit to bleed over into one of the lighting circuits. With the vehicle shut off,...
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  • Trailer Lights Go Out When 2002 GMC Yukon Headlights are Turned On
  • This sounds like 1 of 2 things. Either a bad ground or the vehicle side wiring is being overloaded (which can happen if there are a lot of lights on the trailer). Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be...
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  • Troubleshooting 7-Way on a 2001 Chevy Truck that All Circuits aren't Functioning
  • The first place you will want to check is the fuse box on your 2001 Chevy 2500 Silverado. You will want to look for the trailer wiring fuses and replace them as needed. Since I am not entirely sure what circuits on your truck aren't working it could be you are missing a couple connections under the hood of your truck for the brake controller wiring to be completed. Check out the FAQ article I attached to the right for more info on this. Corrosion in the 7-way connector or on the back...
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  • No Power On 12 Volt Circuit on 7-Way Trailer Connector on a 2006 GMC Sierra 2500HD
  • On some GM trucks, even those with factory tow package, the wiring is not always complete. You may need to manually run a wire from the front of the truck to the back of the 7-Way. I have included a link to the right that should help. It talks about the under the hood connections that might need to be made when installing a brake controller but also mentions the 12 volt power wire. Presumably, if the wire is attached directly the positive terminal, it would have power all the time. But...
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  • Trailer Connected to 2012 Ram 2500 Causes Truck Reverse Lights to Come On
  • The center pin on your 2012 Ram 2500 is probably wired to the reverse lights. The center pin on the trailer is probably wired to a trailer mounted battery or breakaway system battery and it is back feeding to the trucks reverse lights. The trailer could have more than 1 battery on it. What you will need to do is figure out what is wired to that center pin on the trailer side. I have included a picture that shows the pin out functions of a vehicle side and trailer side 7-Way that...
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  • Troubleshooting Running Lights and Dash on 1986 Ford Econoline Jayco Motorhome
  • You said you checked the fuses. Some motorhomes have fuse boxes in multiple locations, inside the engine compartment, inside the cab under the dash, and even in the camper sewer/electrical compartment. Sometimes a fuse may appear to be in good condition, but really needs replacing. To rule that out, take a new fuse that has the same rating and insert it into the proper location. If the problem is a short, and the next fuse that you insert shorts out as well, you will need to use the...
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  • Troubleshooting Dash Lights and Running Lights not Working in 1986 Jayco Econoline Class C
  • Without knowing more about the problem you are experiencing, like whether it's the vehicle that's experiencing the problems or the trailer wiring, the best recommendation I could give would be to check the fuse box looking for running light and dash light circuits and replace the fuses as needed as this would be the most likely cause of the problem you have. Beyond that you would want to track down wiring diagrams of your vehicle to see if wiring is damaged and needs replacing. At this...
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  • Troubleshooting Trailer Running Light Circuit that Quit Working on a Tow Vehicle
  • Sounds like a blown fuse on your tow vehicle. Check out the fuse panel and look for tow package related fuses and check them all. Most likely one will be blown and need to be replaced. I attached an FAQ on 4-way troubleshooting for you to check out as well.
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  • Troubleshooting Trailer Blinkers that Both Blink When Either Turn Signal is Applied
  • It sounds like you have the blinker circuit of your 1998 F150 run to the running lights circuit on your trailer wiring so when the blinker is applied both of your running lights are flashing. Any time you see trailer lighting that illuminates dimly when the wrong circuit is applied is usually indicates that there is a weak ground on the trailer wiring circuit. How that all works is beyond me, but what you will want to do is return the trailer to the previous wiring configuration you...
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  • Troubleshooting Trailer Lights that Don't Function Properly Vehicle Head or Running Lights are On
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal...
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  • Troubleshooting Why Trailer Lights Go Out When You Hit the Brakes
  • It sounds to me like you may have a ground problem. There are several places to look for a poor ground connection. I recommend starting with the trailer connector on the trailer. Check to make sure that the ground wire is secured to a clean metal surface on the trailer. In addition, each lamp/signal will also need to be grounded. Typically the lamp/signal is grounded through the mounting bolts having direct contact with the trailer frame. If the area that the lights are mounted to...
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  • Rental Trailer Caused Fuse to Blow Now Trailer Lights Won't Work After Replacing Fuse
  • It sounds like the rental trailer had a short and caused the fuse to blow. It could have actually caused more than one fuse to blow (or a relay if your vehicle also uses relays for the tow package wiring). Use the vehicle owner's manual to find all fuse and relay locations related to the tow package wiring to see if there is something else that needs to be replaced. To test the vehicle side trailer wiring you can follow the help article I have linked to the right.
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  • Troubleshooting Left Turn Trailer Taillight Not Functioning
  • Without knowing what vehicle you have or what trailer wiring harness you have installed on that vehicle it is pretty difficult for me to say what could be wrong, but since you checked the tow package fuses you have at least ruled that out as well as determined that the problem is most likely on the vehicle side. However, if you haven't already I would recommend you use a circuit tester like part # 3808 to verify that there is not voltage on the left turn/stop circuit when the left blinker...
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  • Troubleshooting 2005 Chevrolet Silverado 1500 7-Way Trailer Connector With No Power
  • Normally, the power wire for a 7-way connector will be coiled up and under the master cylinder if it is not attached already. It should be connected to the post located right by the STUD # 1. You will need to make sure there is a fuse in the STUD # 1 location as well. This should complete the power connection to your 7-way connector. You can use a circuit tester like part # 3808 to test the wire leading into the back of the connector on your 2005 Chevrolet Silverado 1500. If it is receiving...
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  • Troubleshooting Trailer Lights After Installing Hopkins Replacement 4-Way Connector # HM48192
  • The part you referenced, Hopkins Endurance Quick-Fix Replacement 4-Way Flat Trailer Connector # HM48192, has LEDs to indicate the presence of a signal. Since your connector's LEDs are lighting up this tells us that the signals from your tow vehicle 4-way connector are reaching the Hopkins connector. Since none of your trailer lights are working, the most likely explanation is a bad ground. Check the trailer's ground wire that connects to the trailer frame. This will typically be a white...
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  • Troubleshooting Trailer Taillights that Stop Working When Brake Pedal is Depressed
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal...
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  • Troubleshooting a Brake Controller not Working When Used with a 7-way to 6-Way Adapter
  • A 6-Way trailer connector can be pinned in 2 different ways. The center pin can either be 12 volt power or trailer brakes. You will need to determine which way your trailer is wired up and then make sure the adapter you have is wired up the same way. This would explain the issues you are having with the brake controller not working. Next thing you will want to do is test the circuits of the 7-way with a circuit tester like part # 3808 to make sure all of the circuits are active. If so,...
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  • Troubleshooting Trailer Taillight Signals that Stop Working When the Running Lights are On
  • This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal...
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  • Trailer Wiring Harness Left Turn/Brake Light Circuit Keep Failing on a 2011 Hyundai Tucson
  • Since it sounds like this is a recurring problem it might indicate a problem on the trailer, specifically a short or overdraw situation that is causing the failure. The only reason I think this might be the case is because it is unlikely that 2 harnesses would fail in the same way. You will want to check the trailer wiring for any pinched or frayed wires that might be causing a short. Also make sure that the vehicle and trailer side connectors are clean and free of corrosion. Ultimately...
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  • Troubleshooting Trailer Running Lights Function on 2011 Porsche Cayenne Wiring Harness Install
  • The circuit that carries the stop/turn circuit is not the same circuit as the running light circuit. The circuit on the 4-way you have that has a brown wire leaving it is the running light circuit. You will need to test this circuit. If this circuit does not have voltage on it the problem is in the wiring of the harness most likely. You would want to review the install instruction I attached to the right to verify that it is installed correctly. If the voltage is there then the problem...
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  • No Power from Ford Brake Controller to 7-Way Trailer Connector on 2010 Ford F-150
  • I think this might be the ultra-rare Ford dummy harness issue. A few years ago I had a customer with a similar problem. It took days of troubleshooting and a savvy Ford tech at a dealership to determine that the harness behind the dash that the controller plugs into was not a complete harness so that could be what is going on. Ford would have to provide the harness. If you have the correct harness, which is likely given how rare this issue is, then it could be another problem with bent...
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  • No Power to 7-Way Trailer Connector on a 2004 Ford F-150
  • It sounds like a possible tow package fuse has blown on your 2004 Ford F-150. You will want to use the truck owners manual to find the locations of all fuses/relays associated with the tow package wiring to check them. The 12 volt pin on a 7-Way does not affect the regular trailer lights and the fact that everything stopped working with the interior lights is what makes me think the issue is related to the tow package fuses (specifically the one that controls the 12 volt circuit on the...
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  • No Brake Light Signal on 2000 Chevy Silverado Trailer Connector
  • If the 4 pole on the truck is factory installed, and you aren't getting any signal on the trailer connector when the brake pedal is pressed a blown fuse is the most likely culprit. Check the under-hood fuse box for a blown fuse. The lid of the fuse box should have a diagram on it that shows which fuse protects which circuit. If there is a blown fuse, it could have been caused by a short in the wiring of the trailer. Once the fuse is located and replaced, be sure to closely examine the...
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