Trailer Lights Go Out When 2002 GMC Yukon Headlights are Turned On

Question:

when the head lights go on the trailer lights all go out everything works until the head lights go on than nothing to the trailer all of the truck lights work fine either way but not the trailer all fuses are good even under the hood help thanks

asked by: Gregg

Expert Reply:

This sounds like 1 of 2 things. Either a bad ground or the vehicle side wiring is being overloaded (which can happen if there are a lot of lights on the trailer).

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.

If the trailer does have a lot of lights then switching to LED lights would solve the problem of too much power draw.

expert reply by: Michael H