Completing Under Hood Wiring Connections When Installing Brake Controller on 2002 GMC Sierra 1500

Updated 08/02/2012 | Published 08/01/2012

Question:

If this plugs into the factory port under the dash on my 2002 Gmc sierra 1500, what are the red and blue wires under the hood for? What are they supposed to be connected to? The truck has the light duty trailer wiring only, 4 pin flat connector so i know i have to run wires back to the rv plug for brakes and power. However i still dont know where to connect the underhood wires.

asked by: Brian R

Expert Reply:

To install the controller itself, you will first need the # 3025-P wiring harness.

Under the hood, The red wire that provides power for the brake controller needs to be connected to the power post on the fuse box that is closest to the firewall. A 30 amp fuse will need to be placed in the closest fuse location to the post to activate it. The blue wire which carries the brake controller output voltage will need to be extended with a length of 10 gauge wire and extended under the vehicle to the 7-way connector at the rear of the truck. If you need a 12-volt accessory circuit for the 7-way, a 40 amp fuse should be placed in the location closest to the other post. Attach a ring terminal to another length of 10 gauge wire, and run it to the trailer connector.

If you are running two circuits to the trailer connector, one for brake controller output and the other for the 12-volt accessory power circuit, you can use a length of duplex cable, part # 10-2-1 which is sold by the foot.

We have an FAQ article that describes the process for you, to see the article click the provided link. I have also linked you to a video that will walk you through the procedure, start to finish.

expert reply by: Mike L