How to Test Brake Controller Wiring of Vehicle for Wiring to Controller

Question:

I wanted to find out the wiring diagram on the factory port brake controller in my truck. I have brought a Hopkins brake control connector #47755 and found that the wires on the factory does not match to the b.c. connector. I know what the b.c. connector 4 wires, black, blue, red and white is for, but the factory wires on it in order is: small white/tan tracer, large red/orange, large blue, small black/orange. I consulted the book Haynes manual and found that neither wires match to the inch typical wires listed in the book. Do you know where those wires go to and is it messed up in order?

asked by: Ian V

Expert Reply:

You are going to have to test the wires to determine their function and how they would wire to the brake controller. If the colors don't match what the OEM book you have says they should be then the only way is to test to be sure.

One of the wires should have power all the time. That would be the power source for the controller and would run to the black wire. One of the wires should have voltage only when the brakes are applied. That goes to the red wire of the controller. That leaves two wires. The brake output and the ground.

You will need to test for the ground wire. Ground the tester to the constant 12-volt power wire, then probe the remaining two wires. The wire that lights the tester will be the ground, the other will be the brake output circuit.

expert reply by: Jameson C