Troubleshooting Left Turn Trailer Taillight Not Functioning  

Question:

Expert Reply:

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 # PTW2993 to verify that there is not voltage on the left turn/stop circuit when the left blinker is applied.

What I suspect could be happening is that you have a weak ground on the left turn/brake light assembly on your trailer. A different vehicle with a higher amperage trailer wiring system could overcome this weak ground and the light would function, but with your vehicle it wouldn't work.

If the voltage is on the circuit when you tested this would indicate that the ground is insufficient for the taillight assembly. You would want to check the condition of the ground on this light assembly. You will want to make sure it is attached to a clean metal surface. Most assemblies ground through their mounting hardware.

If the harness is an aftermarket one make sure that it is installed properly and all of the connections are being made securely. If a converter box is on the harness you can test it like the video I attached shows.

There could be damage to the wiring somewhere on the circuit of the connector as well. You should trace the wiring back from the connector on your vehicle looking for cuts or exposed wire and fix as necessary.

I attached a couple helpful FAQ articles to the right for you to check out as well.

expert reply by: Jameson C

0