Troubleshooting Ford F-350 Trailer Brake Controller Not Registering

Updated 03/22/2010 | Published 03/19/2010

Question:

light of trailer work perfectly but controller not registering checked fuses all good dont know what to do

asked by: andrew b

Expert Reply:

I would start by using a circuit tester, item # PTW2993 if needed, to check the wiring going to and coming from the brake controller. There are 4 wires that will need to be checked.

White - Ground
Red - Stoplight Switch
Black - 12 Volt Constant Power
Blue - Brake Feed to Trailer Brakes

First, make sure the ground wire is attached to a clean, paint and rust-free chassis ground. Next, connect the circuit testers alligator clip to the ground and check the black 12-volt wire going into the brake controller. Next, check the red wire coming off of the stoplight switch which should have power only when the brake pedal is pressed. Finally test the blue, brake feed wire.

If you have power going into the controller on the 12-volt wire and the red stoplight wire, when the pedal is pressed, then you should get power out on the blue wire. You should also get power out on the brake feed wire when the manual brake lever is activated.

If the above connections are made properly and the controller is still not working, disconnect the blue brake feed wire near the back of the brake controller. Then check the blue brake feed wire for output. If the the controller functions normally when the brake is pressed, you have a problem on the brake circuit somewhere between the controller and the trailer brakes. If you still have a problem, then there is most likely something wrong inside the brake controller itself. Brake controllers have no internal user serviceable parts.