Wiring a Brake Controller to My 2003 Chevrolet Trailblazer

Updated 08/12/2009 | Published 08/10/2009

Question:

my 2003 Trailblazer is pre-wired for towing and the wire labels under the dash are listed: aux batt grnd chmsl. Can you pls tell me which vehicle wires go to which color coded controller wires? Do I have to connect the red controller wire to the stop lamp circuit and if so, where is that connection best made?

asked by: Bob F

Expert Reply:

The wiring on the brake controller is as follows. White is the ground wire, black is the 12-volt power wire, red is the stoplight switch wire and blue is the wire that goes to the trailer brakes. Your under-dash wiring should be tested with a circuit tester, part # PTW2993, if you need one, to confirm each function before wiring the brake controller.

The standard colors for Chevrolet are Red is the 12-volt wire that goes to the black on the break controller, light blue is the stoplight wire that goes to the red wire on the brake controller, black is the ground wire that will attach to the white wire on the brake controller and dark blue goes to the trailer brakes and is attached to the blue wire from the brake controller. Manufacturers change these colors periodically for seemingly no reason so you will need to verify the function for each wire before wiring the controller to the vehicle.

The lables on the wiring are there for reference and may be correct but I always double check to be sure. I believe the aux wire will be the trailer brake output and should be a heavier gauge wire, the chmsl wire will be the stoplight switch wire, batt will be the 12-volt input to the controller and the grnd will connect to the ground wire.

expert reply by: Robert G