Left Trailer Brake Light Does Not Work But All Other Lights Do

Updated 04/07/2015 | Published 04/05/2015

Question:

I bought a travel trailer but when I hooked up my 2003 yukon to tow it the left brake light doesnt work. The trailer lights are all functional when hooked up to my brothers truck. The left turn signal works but not the brake light.any idea where the problem could be?

asked by: Tom

Expert Reply:

It is strange any time a turn signal works but the brake light on the same side doesn't. this is because the brake and turn signal lights are on the same wire/bulb. The usual culprit is a bad ground.

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