Troubleshooting Malfunctioning Trailer Lights Caused By Poor Ground Connection

Question:

Turn and running lights work. When I apply my brakes they go out. Help thx

asked by: Bryce

Expert Reply:

From what you describe, it sounds like you have a ground problem somewhere in the trailer wiring or on the trailer wiring harness installed on the vehicle. Ground problems will make the trailer lamps do all sorts of wacky things. With the running lights and the brakes on, activating the turn signals will draw maximum amperage through the trailer wiring system. If you have a ground problem, that's when it will typically show itself.

Check that the trailer connector on the vehicle is securely grounded to clean metal, ideally on the trailer frame. On the trailer, the trailer connector should be grounded somewhere on the trailer tongue, the connection should be secure and not corroded. Each trailer lamp should ground either via a separate ground wire attached to clean metal on the trailer frame or by its mounting bolts being in direct contact with the trailer frame. Check the bulb sockets, and make sure they aren't corroded.

I'll also link you to our trailer wiring troubleshooting article, I hope you'll find it helpful.

expert reply by: Mike L