Trailer Brake Lights Not Working with Curt Wiring Harness Installed on 2009 Hyundai Sonata

Updated 07/25/2016 | Published 07/23/2016

Question:

Just installed the Curt light kit 56049 on my 2009 Sonata. None of the lights seem to work on a new trailer I just bought. Traced it down to both tail lights not being grounded properly. No one cleaned the paint off the connection point. After getting the ground connects correct, I rechecked everything. The turn lights, side lights and tail lights work fine now. The brake lights DO NOT work. This doesnt make any sense to me. Can you point me in the right direction.

asked by: Greg B

Expert Reply:

It could still be a ground problem. 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. Since the brake lights draw more constant power than any of the other functions it makes sense that a ground problem would show up when using the brakes.

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. Make sure that the converter on harness # C56049 is also grounded to a bare metal spot on your 2009 Hyundai Sonata. Grounding it by itself and not with other electrical components yields the best results.

The light grounds on the trailer 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