Brake Controller Wire Functions By Wire Color
Updated 06/05/2026 | Published 10/26/2009
Question:
i have a kelsey energizer brake controller, the wires aint mark what goes to what, i have a blue one, a black one, a red one, and a white one, the colors are the same for my harness that plugs in under my dash
asked by: frank
Expert Reply:
The wires exiting the rear of your controller serve the following functions. The blue wires carries the brake output from the controller, the white wire is the ground, the black wire supplies 12 Volt power, and the red wire is tied into the vehicle brake wiring. If the wiring adapter you have is an aftermarket harness, it should wire up color for color. To the right I have attached a picture of a diagram of how brake controllers wire to tow vehicles.
To be safe, I would suggest using a circuit tester such as part # PTW2993, to verify the connections. Without wiring the controller, plug in the harness. Test the socket for the black wire to verify the presence of voltage, test the socket for the red wire to verify that it gets voltage when the brake pedal is pressed. If this checks out, it would be safe to wire up the controller.
Sailingbum
6/5/2026
My brake controller has the wires you mentioned. Black red blue and white. It also tells me which ones go to wear on my vehicle. The problem is is I have four wires hanging under my dash on a 2014 Yukon Denali and they are yellow, white, blue, and red. So which hooks to what because the diagram you showed me is not gonna help me. Because I look at your diagram and I’m not going to Chase wires back to find out which one goes back to where. It should be understood which wires hanging go to which wires on the controller. In other words, the blue goes to the blue probably because they both go to the Trailer. The red off of the controller says it’s for the brake switch, but is that the red hanging on my car? So here’s what I have. I have the brake controller standard wire colors but the wires hanging on my car. We’re not labeled like previous cars. I’ve done the same thing too. I did this to a 2010 Chevy avalanche and they were marked which wire went where these were in a bundle when I un taped them, they didn’t have labels and that that’s my problem.
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Perry
6/22/2020
I have a hydraulic brake controller only has three wires? Blue, black, red, how am I going to ground this