How to Find Which Wire to Connect Red Wire From Brake Controller to on Motorhome with Air Brakes

Question:

I have a 2003 Monaco Knight with air/hydraulic brakes. Going to install a brake controller there is a black, white, red, blue wires on the controller. I know where the black , white, blue wires connect to, cannot find where the red wire connects to. Does not have brake a switch on the brake pedal, but it has a air pressure switch with three wires blue,red,black. Need to know which wire to connect to Thanks P.S NO factory Harness

asked by: Rey

Expert Reply:

To install a brake controller, like the Prodigy P3 # 90195, that comes with the Black, White, Red, and Blue wires you will need to splice them into the following functions:

Black - Battery for Power (be sure to install the circuit breaker as well)
White - Ground
Red - COLD Side of the Stop Light Switch (only receives a signal when the brake pedal is pressed)
Blue - Run to 7-Way to activate trailer brakes

What you will need to do is find which of those wires receives power only when the brake pedal is pressed. You can do so using a Circuit Tester # PTW2992. This will make it so that your brake controller only receives the signal when the pedal is pressed which will also carry over to the brakes on your trailer. Since most trailer companies do not keep a record of what color wire is used for certain applications a circuit tester is your best option.

expert reply by: Jon G