Right Turn Signal, Brake, and Tail Lights Do Not Work on Trailer Towed by a 2001 Ford F-150

Question:

I have the 7 way trailer tow system and I only had left turn signal and left tail light. How do I determine where the problem is?

asked by: Pat Q

Expert Reply:

This is most likely a ground problem since it is just the one side that is working. First, disconnect the trailer and use a circuit tester, like # PTW2993 if needed, to test the pins on the truck 7-Way connector. If you do not have the right turn signal/brake lights at the 7-Way, then there is a wiring problem on the truck that could be a fuse or relay.

But, since it is also the tail light that is not working just on the one side, chances are it is a ground on the trailer. Make sure that the trailer and truck connectors are clean and free of corrosion. Then make sure the main trailer connector ground and the grounds for the lights on the right side are all attached to clean and corrosion free bare metal surfaces.

expert reply by: Michael H