Location of Wire for Third Brake Light on Camper Top of 2010 Sierra 2500HD

Question:

I am trying to locate the location and color of the wire provided to add a third brake light to a 2010 gmc sierra 2500 hd for my topper. Thanks

asked by: Gary M

Expert Reply:

Look under the dash for the dedicated brake light wire. It will be situated below and left to the steering column. Find the bundle of wires held together with white tape. The tape should have the functions of the wires on it. The wire you need is likely light blue. Test it with a circuit tester, like # PTW2992, to be sure it is the correct one. It should only show a signal when the brake pedal is pressed.

If that wire is used by a brake controller, look at the brake switch located above the brake pedal. You will find numerous wires going in and out of the switch. You will need to test the wiring using a circuit tester to find the one that only carries a signal when the brake pedal is pressed. If it shows a signal with the lights on or turn signals engaged, it is not the correct wire.

Either of these locations will require routing the wire out of the cab through the fire wall through an existing grommet or by drilling a hole. Be careful when drilling because there may be components on the other side of the fire wall, and you would not want to drill into them.

expert reply by: Chris O