Where to Access the Third Brake Light Circuit on a 2008 Chevy Silverado/GMC Sierra 1500

Updated 12/02/2013 | Published 11/29/2013

Question:

My Sierra is a 2008 1500wt. Can I get instructions on running a signal to the third brake light on the cap? I have read many post but none seem to apply to my truck. I have a factory installed trailer hitch and the GM electrics jack at rear bumper. Need to get truck inspected this month so need the light for sure. Looked under my truck and found a heavy blue wire marked electric brake going into my trailer connector. I do not have brakes for the trailer so could I use that blue wire to power the chmsl on my cap? Thanks

asked by: Steve F

Expert Reply:

First, the wire for electric trailer brakes is not going to work because it will only have power when used with a brake controller. The one place I know for sure to access the CHMSL circuit is under the dash. You will need to look for a wire bundle under the dash, to the left of the steering column. There should be a white tag holding the wire bundle together.

There should be an orange wire and that is the CHMSL wire. You can attach a length of wire to this orange wire, route it through the firewall, under the truck, and to where ever it needs to go on the camper shell. Be sure to avoid areas that may pinch or burn the wire. You can use zip ties to secure the wire to the under side of the truck.

Another option is to check with a local place that sells/installs camper shells. They may know of an easier place to access the CHMSL wire closer to the camper shell.

expert reply by: Michael H