With Trailer Running Lights On, All Lights Go Off when Applying Vehicle Brakes

Question:

trailer lights were working fine now when i apply the brakes with my lights on they all go off, And also when i put my 4ways on all the lights flash. I need help please thanks

asked by: Rich

Expert Reply:

The problem with the lights going off sounds like a ground issue. The brake lights apply additional load on the wiring and this is usually when a ground problem will show up. First, make sure that the trailer connectors are clean and free of any corrosion. Corrosion can cause a short which can lead to many problems, including the flashing problem.

On the trailer side, make sure the main ground wire from the trailer connector is attach to a clean and corrosion free bare metal surface. The trailer tail lights usually will ground through the mounting studs, unless they have a ground wire. In either case, they should be attached to clean and corrosion free bare metal surfaces.

You can also check the wiring on the trailer from the connector to the tail lights. look for any nicks in the wire, breaks, or loose connections. If any of the copper is exposed and making contact with the trailer frame, this can cause a short circuit.

expert reply by: Michael H