Troubleshooting Trailer Lighting That Stops Working with Headlights On

Published 06/18/2021

Question:

OK, I got running lights.a good left turn signal,although i cannot get the right turn signal to work! i swapped lights so it is not a bad bulb and i have tried switching wires to no avail!! I do appreciate the prior answerand u were right about the bad ground! Thank U !!!!

asked by: John K

Helpful Expert Reply:

Your main problem is an insufficient ground for the trailer wiring. Try improving the connection of the main ground wire of the trailer wiring harness. Make sure it is attached to a clean metal surface. Or you can run all of the trailer wires back to the main ground. This is actually the ideal solution. But you can also check the current grounds for the lights to make sure they are making a solid connection to a clean metal surface.

What you described is the classic insufficient ground scenario so finding a way to improve the grounds will fix the problem. The issue is that when your headlights are on the maximum amount of amperage draw is put on the setup which if there's an insufficient ground this would be when this would show up.

expert reply by: Jameson C

John P.

6/18/2021

Jameson C.

6/18/2021

Does the brake light work on that side? If you haven't checked already I would recommend taking sandpaper to all of the pins of your trailer wiring to see if there's any dirt or corrosion that you can clean off. I bet that gets takes care of the problem.