Troubleshooting Trailer Wiring that Stops Working When Headlights Are On

Updated 11/16/2015 | Published 11/15/2015

Question:

My trailer lights all work when the headlights are off. I figured it was a ground wire problem and created a new clean connection. Everything still works with the headlights off, but when I turn them on only the trailer lights on the drivers side work. Any ideas?

asked by: Terelyn

Helpful Expert Reply:

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.

expert reply by: Jameson C