Trailer Running Lights are Not Working

Question:

RUNNING LIGHT ON TRAINLER DOES NOT WORK

asked by: JAMES P

Expert Reply:

There are a few things that could be causing the problem with the trailer side running lights. To determine if the issue is on the vehicle or trailer side you will start by testing the vehicle side trailer connector using a circuit tester such as # PTW2992. I have included a couple of links to the right that explain how to test.

The issue could also be on the trailer side. Most likely it would be a damaged wire or a bad ground. 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.

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