Location of the CHMSL Circuit on a 2012 Chevy Silverado for a Camper Shell Third Brake Light

Updated 10/16/2013 | Published 10/14/2013

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Question:

I have read several similar questions and replies on your site regarding how to wire a third brake light and dome light in a truck cap. Some answers mention a light blue wire that is not hooked to anything that can be used for the brake light. Does the 2012 GMC Sierra have this extra wire? Have I not looked far enough back along the harness or could it be located somewhere else? Great site and excellent products. Thanks!

asked by: Larry G

Expert Reply:

There is a bundle of wires under the brake pedal of your 2012 GMC Sierra that will have an orange wire that should be used to power the third brake light of the camper shell. I have also read that the light blue wire under the rear of your vehicle in the harness near the trailer connector will also work, but I would recommend you use a circuit tester like our # PTW2993 to make sure that this wire only sees voltage when the brakes are applied and none when the blinkers are on without the brakes.

We do not have any specific info on the blue wire, but you might keep looking to see if you can find it.

Check out the FAQ article I attached that will show where the CHMSL wire is.

expert reply by: Jameson C