Troubleshooting Turn Signal Not Working on Trailer After LED Taillight Installation

Question

Question:

Led tail lights have three wires black green and white which directly match what is coming off of the trailer. I’ve connected the wires using crimp style connectors and heat shrink tubes. I’ve checked all of the fuses and relays on my pick up 2016 f250 super duty. Just for clarification I do know there are two fuse boxes. I’ve checked both and all fuses and relays are good. I still have no directional lights on my tail lights. One thing that confused me as all get out. When I turned my hazard lights on the tail lights wouldn’t flash but the license plate light that’s integrated with my right tail light started flashing. I’ve got running lights. No hazards no turn signals either side and no breaks either. When I do utilize my Left turn signal the trucks lights flash rapidly as if there’s a burnt bulb somewhere, there isn’t. When I utilize my right turn signal it flashes normally on the truck but nothing on the trailer.

asked by: Julian K

0

Expert Reply:

Based on what you have said, something is off from the installation of the new LED taillights. When it comes to 4-way wiring like the 4-Pole Trailer End Connector # 18004, the right turn signal/stop and left turn signal/stop run on the same circuit. Since you indicated that the brake lights are working the turn signal should as well unless the wiring is off from your light installation. I would recommend double checking the wires to make sure they are correct. I would also make sure that the ground connection is secure.

expert reply by: Robin H

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Julian K.

10/27/2021

Led tail lights have three wires black green and white which directly match what is coming off of the trailer. I’ve connected the wires using crimp style connectors and heat shrink tubes. I’ve checked all of the fuses and relays on my pick up 2016 f250 super duty. Just for clarification I do know there are two fuse boxes. I’ve checked both and all fuses and relays are good. I still have no directional lights on my tail lights. One thing that confused me as all get out. When I turned my hazard lights on the tail lights wouldn’t flash but the license plate light that’s integrated with my right tail light started flashing. I’ve got running lights. No hazards no turn signals either side and no breaks either. When I do utilize my Left turn signal the trucks lights flash rapidly as if there’s a burnt bulb somewhere, there isn’t. When I utilize my right turn signal it flashes normally on the truck but nothing on the trailer.

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Robin H.

10/28/2021

If you have not checked the ground connection still I would start there. The majority of the time bizarre things like this are related to a poor ground connection. I would also check the ground on my 4-way wiring on the vehicle and the trailer. Make sure the connection is secure on a clean, bare-metal surface. I would also go ahead and inspect the 4-way connectors and make sure they are clean and there is no visible damage. I don't know what lights you have, but it is also possible the wiring colors are not an exact match. If you want to test out the function of the different wires to attempt to ensure that they are correctly matched to the lights you could use a circuit tester like the # PTW2993 or just attempt to change the connections and see if it makes a difference. By checking the wires at the back with the circuit tester you will also be able to tell if the signals and other lights are working properly. If everything is coming through from the trailer wiring it has to be an issue with the lights. Outside of those two things, you may have a short in the wiring. You can also use the circuit tester to check for this. I would start at the 4-way connection and work my way along while inspecting the wiring. Repair any damage to the wiring as needed. It is also possible that you need to add load resistors on the circuits after the installation of the lights. If nothing else works I recommend installing the Load Resistor Kit for LED Turn Signals # DI34ZR. I have attached a link for a helpful article on troubleshooting 4-way wiring for your reference.

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