Right Side Trailer Lights Do Not Work, Grounds are Clean

Question:

I have cleaned the grounds on the both tail lights ,the right side light will not work at all.

asked by: Philip B

Expert Reply:

There are a few things you can check. First, disconnect the trailer and use a circuit tester like # 3808 if needed to test the trailer connector just to make sure everything is working fine. If the left side lights are working, chances are the problem is not on the vehicle.

But if you do find an issue on the vehicle side then it could be a relay or fuse (consult owners manual for locations) or a bad ground in the wiring harness.

On a lot of trailers, there is a jumper wire from one side of the trailer to the other side for the running lights. Trace the wiring back and make sure that connection is made and that there are no broken or exposed wires touching bare metal.

If you recently added a plastic license plate, this can cause a bad ground connection. Make sure to check the trailer side and vehicle side connectors for any dirt and corrosion and clean them out. Make sure the main ground is attached to a clean metal surface.

If you have a large number of lights on the trailer, it is possible that the power draw is too much for the wiring harness and that would cause some lights not to work.

expert reply by: Michael H