Trailer Brake and Turn Signals Do Not Work when Running Lights are On, 2011 Kia Sorento

Question:

i bought this item and followed the steps to install. When i plug in my trailer the turn the headlights on the trailer lights come on however the brake lights and turn signals do not work. If I turn my headlights off the brake lights work the left turn signal doesnt work and the right turn signal makes all of the lights on the trailer flash. Do i need to return the unit? What could be the problem?

asked by: Kolby

Expert Reply:

It sounds like there is a ground issue that is causing the malfunction. First, you can do some tests on the vehicle side to see if it is the problem or if it is on the trailer. You will need a circuit tester like # 3808 if needed to test the wiring.

Disconnect the trailer from the vehicle and use the circuit tester to test the wires that go into the converter from the vehicle. Using the circuit tester, have someone run through the brake, turn, and running light functions while you test the wires. If the signals are not correct coming into the converter then there is a problem with the vehicle wiring.

If the signals are correct, test the 4-Way connector for the correct functions. If they are not correct coming out to the 4-Way then there is something wrong in the converter and it will need to be replaced. If the signals are correct, then that would indicate a problem on the trailer side and not with the vehicle or converter.

To test the trailer, start by checking the 4-Way connector for corrosion and clean it out. Check the main ground from the trailer connector and make sure that it is attached to a clean and corrosion free bare metal surface. You will then want to do the same with each of the trailer lights.

There is also a possibility that the trailer lights are drawing more power than the system can handle. The harness is rated for 2.1 amps per side for stop and turn lights and 5.6 amps total for running lights.

expert reply by: Michael H