When Trailer Connected to 2002 Ford F-350 Trailer Lights Do Not Work

Question:

I have a 2002 ford f350 and I am having problems with trailer lights. The voltage s when i turn turn signals on at trailer connector. The trailer only has lights when connected and turn and brakes lights do not work. I have checked the trailer separately and it has no issues. The voltage goes from 12 to 10 at connector? The lights show 13 volts at connector. I have cleaned plugs and no luck. The relays are clicking with turn signals on. Fuse was pulled from under dash and is fine. All truck lites work? Im at a loss? Help?

asked by: Vincent B

Expert Reply:

This sounds partially like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

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. Even if the pins in the connectors are clean, corrosion can build up inside the connectors where the wires attach so checking inside the connectors is important.

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.

expert reply by: Michael H