Troubleshooting Trailer Wiring that Left Stop/Turn is Dim

Question:

Hello, I have a 2007 Frontier with the 7 pin Factory towing kit. When plugging in a 4 pin adapter the built in tester says everything is working. When plugging in a set of tow lights they are not working correctly. No left turn signal, when hitting brakes left side dims while right gets extremely bright, uneven brightness on running lights. I tried swapping the relay Passenger kickpanel to the other connector and while both signals and brake lights work there are no running lights. I have tried cleaning up the ground connections in the hood area, none in rear of vehicle as the 7 pin connects directly into a harness on the body. Is it possible one of the relays is bad?

asked by: Tim

Expert Reply:

Since the trailer wiring on the vehicle has checked out with a tester it would seem that the problem is actually on the trailer. It sounds like you are experiencing a ground problem.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

I attached an FAQ on troubleshooting 4-way installs for you to check out as well.

expert reply by: Jameson C