Finding the Cold Side of the Stop Light Switch on a 2017 Toyota Highlander

Updated 08/29/2017 | Published 08/28/2017

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Question:

Is there any way to hook up to the hot side of a brake switch without going under the dash to get it? Maybe in the back compartment? Thanks

asked by: Don

Expert Reply:

I believe that you are trying to connect to the cold side of the brake light switch. The hot side wouldn't do you any good, but the cold side is what you would connect a brake controller like the Tekonsha Prodigy P2 # 90885 to.

Your best bet is to locate the cold side of the stop light switch under your driver side dash but using a Circuit Tester # PTW2993. The cold side of your switch is the wire that only gets hot when the brake pedal is pressed. If you look at the attached video starting at the 20:50 mark you will see one of our install team members finding the stop light switch on a 2015 Toyota Highlander. It might not be the exact same color as the wiring on your 2017 Highlander, but it should be in a fairly similar location. You will want to still test the functions with a tester.

If you are still having trouble locating it, you can try to trace the wire from your third brake light which gets its connection from the stop light switch at all. Since a brake controller requires more power than your third taillight it will do you no good to splice into that wiring.

expert reply by: Jon G