What is the Red Wire Function on an Electric Trailer Brake Controller

Updated 05/19/2020 | Published 05/24/2011

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Question:

The red wire from thye controller what wire does that connect to on the truck side it shows red+ does it go to a constant hot or the wire that powers up when the brake is applied. Thanks

asked by: Glen

Expert Reply:

The red wire on the brake controller connects to the stop light wire on the brake switch located above the brake pedal. You will need to use a circuit tester like # PTW2993 to probe the wires. You need the one that shows a signal ONLY when the brake pedal is pressed. If you find a wire that has a signal when the headlights are on or when the turn signals are engaged, it is not the correct wire.

Brake Controller Wire Colors and Functions:
The white wire is ground
The blue wire is output to the trailer brakes
The red wire connects to the stoplight wire on the brake switch
The black wire provides 12 volt power to the controller

If you were to connect the red wire to the battery it would apply constant output to the brakes. I have included a link to our Brake Controller FAQ article for you to view.

expert reply by: Michael H

Michael P.

5/16/2020

I have installed and set up a trailing wiring kit, but the red wire has become pulled out of the control box. Is there a way to reconnect the power line into the control box?

Chris R.

5/19/2020

Are you referring to the actual brake controller? There may be a way to attach that red wire again, but I would need to know what specific model you have.