Troubleshooting Trailer Turn Signals that Only Work When Brake Pedal is Pressed

Published 06/03/2014

Question:

When I plug my tow vehicle into my trailer, the running lights and brake controller work fine. But the turn signals only work once the brake pedal is pressed. However, this can be intermittent because sometimes the brake light wont light up either. But when I plug a different vehicle into my trailer, everything works fine. Even when I plug my vehicle into another trailer, everything works. Do I have a faulty connection or ground on my tow vehicle?

asked by: Bob H

Expert Reply:

Bizzare behavior like what you described is almost always ground related.

I would first start at the trailer tail light assemblies and make sure they are grounded to a clean metal surface. A lot of taillight assemblies ground through the mounting hardware, so you should check to make sure the assemblies are connected to a clean metal surface. Next check that the ground strap of the 4-way on the trailer is connected to a clean metal surface of your trailer.

Lastly check to make sure the ground strap of the Curt Wiring Harness part # C56078 is attached to a clean metal surface. I attached an FAQ on 4-way installs and trailer wiring in general for you to check out.

expert reply by: Jameson C