Should there be Power on a Brake Controller Blue Wire with the Brake Pedal and No Trailer Attached


on a 2002 f250. when connecting to facorty harness should the blue wire light up when u push on the brake pedal, same as stop light prong would?


Expert Reply:

Provided there is a trailer connected and the brake controller was set to the proper output then you should see voltage on the blue wire when you apply the brakes or the manual override. Without a trailer connected, the controller will not send power back unless there is a short (something drawing power on the blue wire).

The brake output circuit will not show a signal at the plug when the brake pedal is pressed and the controller NOT installed. So if you are just testing at the factory connector then there should be no power on the brake circuit.

For a 2002 Ford F-250 and controller # 5100, you would use wiring harness # 3035-P. I have included some links explaining the installation for you. It is not likely that the factory wiring harness wire colors will match up to the brake controller wires color for color.

the controller has the following functions: white is ground, black is 12 volt power, blue is output to the trailer brakes, and red is input from the brake switch.

expert reply by:
Michael H

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