Left Side Trailer Lights Not Working when 2015 Mazda CX-5 Running Lights are Turned On

Question:

My wiring harness was easy and great to hook up but having a issue. It works great when lights are not turNed on but once lights are turned on the left trailer lights do not work. I am thinking its a ground problem.

asked by: Jason F

Expert Reply:

This does sound 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.

expert reply by: Michael H