Troubleshooting Brake Controller that Locked Brakes Up When Travelling Down Hill

Question:

Ive used this Reese pilot controller for several years satisfactorily. Yesterday has Im going down a mountain slope it engaged the brakes on its own. I had to unhook all my lights and wires to get it to release. What would cause it 2 engage without me hitting the brakes or manually operating the controller

asked by: Bradd

Expert Reply:

It's possible the brake controller had an internal problem which would explain why it locked your brakes up but more likely is that there was an issue with the wiring of the controller. Most likely you have a short between the red and black wires of the controller. The red wire is the stoplight circuit for the controller which tells it that you are applying the brakes and the black wire has voltage on it at all times as it powers the controller. If these two circuits short out to each other the controller will lock the brakes up. So check to see if there is a short between these two circuits.

If you can't seem to find the problem here's how to test the controller:

Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # PTW2993, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.

I am including a link to a video that will show you how to test the wiring on a brake controller.