One Running Light On Trailer is Not Working, All Other Lights Working Fine

Question:

I replacing a light on my trailer. Everything else works but when I hook up the new light I can only get the turn signal and brake light to work not the tail light. All over lights working good.

asked by: Mathew

Expert Reply:

If just one running light is not working that indicates a ground problem. 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. But they can show up any time.

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.

expert reply by: Michael H