Left Side Trailer Lights Do Not Work When Vehicle Lights are On

Updated 04/14/2015 | Published 04/11/2015

Question:

All the lights work until I turn car lights on then drivers side trailer light doesnt work . Any idea whats wrong

asked by: Dale

Expert Reply:

This sounds 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.

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 have included a link to a help article that explains how to test wiring as well.

expert reply by: Michael H