Brake Controller Suddenly Stopped Working

Updated 07/07/2017 | Published 07/06/2017

Question:

Green light on but goes off when brakes are applied. No trailer brakes. When sliding controller manually the green light goes red and brakes hum on trailer but no brakes. Ground wire is hot on trailer when applied this way. Brakes on trailer work when emergency flashers are on. Controller installed eight years ago and have worked on this trailer always before.

asked by: Ken

Expert Reply:

The first thing you will want to do is attach the tow vehicle to a different trailer to see if the problem persists. If the problem still occurs, then the error is on the vehicle side. If the problem is not present, the problem is on the trailer side.

If the problem is on the vehicle side, you will first want to ensure there is no dirt or debris in the trailer connector. You will then need to begin checking each of the wires using a circuit tester part # PTW2993. Sever the blue wire about 6" back from the the brake controller to ensure the controller is working. If the controller is working properly, you will then need to test the blue wire just before the trailer connector on the vehicle side to ensure power is passing through the wire. If power is not reaching the trailer connector on the blue wire, you will need to begin tracing the wire back to the controller checking for breaks or frays.

If the problem is not on the vehicle side, you will again want to ensure there is no dirt or debris in the trailer connector. Then you will want to begin testing the wires on the trailer side wiring harness. I have attached our trailer wiring help article for you. You will also want to check that the ground wire is properly secured to a bare metal surface on the trailers frame.

expert reply by: Conner L