Troubleshooting and Repairing Weak Ground Connection on Trailer

Updated 09/26/2020 | Published 09/24/2020

Question:

2006 Saturn Vue. My LED trailer lights are nice and bright. They stop functioning correctly when I turn the lights on. If the lights are off and I step on the brake or I put the turn signals on its fine. when I turn the lights on and the vehicle its hard to tell the difference in my LED lights if theyre on or off. Theyre only on like a little bit. You cant tell the difference if I step on the brakes or anything. Again they get nice and bright if I step on the brake or use turn signals as long as the lights are off on the vehicle and I dont know whats wrong.

asked by: James E

Expert Reply:

So everything is operating normally until you turn on the headlights, right?

This is a classic case of a poor ground connection. Things will work fine until the running lamps are activated, which pulls more amps through the system. If there's a problem, that's when it'll show up.

Make sure the trailer connector on the tow vehicle is properly grounded to the vehicle frame or chassis and that the connection isn't corroded. From the trailer connector on the trailer, trace the white ground wire to its grounding point on the trailer tongue. Make sure the connection is secure and not corroded. Each lamp will ground to the trailer frame either via its mounting studs or via a separate ground wire attached to the trailer frame, make sure all those connections are clean and secure.

For a bulletproof ground connection, I like to remove the ground screw and sand down a dime sized area around the screw hole down to bare metal. I then sandwich a star washer between the ring terminal on the ground wire and the ground screw. The star washer bites into the metal, ensuring a good connection. Then, give the ground screw a quick shot of rust inhibiting spray paint to protect it.

I've linked to our helpful trailer wiring troubleshooting article.

expert reply by: Mike L