Troubleshooting Black Wire on Trailer Brake Controller that Only Gets Power with Brake Pedal

Updated 04/30/2019 | Published 04/27/2019

Products Featured in This Question

7- and 4-Pole Trailer Connector Socket w/ Mounting Bracket - Vehicle End

(2638)

$43.28

Hook Probe Circuit Tester

(60)

$12.41

Question:

Electric brakes not working shows power off the brake controller but not to the seven prong plug-in I am hooked the blue wire to run a new wire back and I lost all my power to the controller the black power wire only shows power when I hit the break pedal hook the blue wire back up and only shows power when I hit the pedal not the manual on the controller Number six fuse shows good that’s wired with the harness under the dash all the wires are marked like they should be hooked up but I’m lost right now why it does not work right

asked by: Arlie P

Expert Reply:

The black wire coming from your brake controller should be ran to the positive post of the truck's battery. This is what actually powers the controller and the wire, if hooked up properly, should always have power. The fact that it's only receiving power when the brake pedal is depressed can really only mean that it's been attached to the wrong circuit and not the battery.

I simply recommend tracing the wiring from the controller to make sure all the correct connections have been made. The red wire from the controller should be connected to the brake light switch wire behind the brake pedal that ONLY gets power with the brake pedal depressed and no power with any other function. You will want to use a circuit tester like # PTW2993 to verify you have the right wire.

The blue wire is what gets ran to the 7-Way for brake output (it sounds like you have this routed appropriately) and the white wire is for ground, which just gets attached to clean, bare metal surface.

expert reply by: Chris R