Troubleshooting Trailer Lights that Don't Function Properly Vehicle Head or Running Lights are On

Question:

I have a utility trailer that the lights have always worked fine on, now all of a sudden I am having an issue were when my running lights are off I have a signal light and brake light but when im towing and need headlights and running lights, the running lights work but I then dont have a brake or signal light. Iv never had any issue like this and was seeking advice. Thanks Also I thought maybe it was something wrong with the plug on my truck but iv plugged my boat and other utility trailer up and they work great

asked by: Ray W

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.

expert reply by: Jameson C