Trailer Lights Not Working and Brake Lights Only Work with Ignition Turned Off

Question:

1999 Chevy K1500 - I have the proper connector changing a 4 wire flat vehicle to a 6 wire trailer. Everything worked great last weekend. I hooked it up last evening and it is not working properly. The brake lights work only when the ignition is off and non of the other lights are working at all. Any idea what the issue may be? Thank you!!!

asked by: Nick H

Expert Reply:

This sounds like a ground issue and possibly a short somewhere. 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 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.

Inspect the wiring on the trailer and truck side (as much as you are able) and fix any broken or pinched wires.

expert reply by: Michael H