Installing a P3 Brake Controller on a 1991 Freightliner Truck

Question:

Is there a wiring diagram for a 1991 freightliner COE?

asked by: Doug R

Expert Reply:

There isn't a specific wiring diagram to install the P3 brake controller # 90195 on your 1991 Freightliner but I can tell you the functions of the wires. The white brake controller wire is ground and needs to go to the negative battery terminal. The black wire is for 12 volt power and goes to the positive battery terminal via a circuit breaker. For some extra wire and a circuit breaker you can use kit # 5506.

The blue wire is output to the trailer brakes. The red wire could be a little tricky if your Freightliner has air brakes. Normally the red wire attaches to the cold side of the brake switch to a wire that only has power when the brake pedal is pressed and not with the headlights or turn signals on. Normally to find this wire an installer would use a circuit tester such as # PTW2993.

It is possible that you would not find this wire on your Freightliner. The other option is to use the owners manual to find a stop light fuse and then use a fuse tap. The brake controller red wire has to be connected to a dedicated brake light only circuit for it to work.

expert reply by: Michael H