Should Stop Light Switch Wire On Trailer Brake Controller Have Ground Or Power?

Question

Question:

I read Mikes response about 2005 GM truck. What he didnt cover is the wire going to the brake switch. When the pedal is pressed is this supposed to be a grounding signal or power signal to the brake controller. Mine is grounded out 100. I even disconnected the wires off of the stop light switch and it is still grounded. I am working on taking the harnes apart to try to figure out what is going on.

asked by: Dan W

0

Expert Reply:

The red wire on the trailer brake controller that goes to the cold side of the stop light switch is a power wire, and should not be grounding. This wire gives 12 volts of power only when the brake pedal is switched, and is what tells the controller to send power to the electric brakes.

On your 2008 Chevrolet Suburban this wire is the light blue/white wire. I recommend double checking that you hardwired the controller to the factory run wires under the dash correctly, as it sounds like a connection got mixed up.

I included a video of a trailer brake controller being installed on a 2010 Chevrolet Silverado for you to watch, as the color of the factory wires and installation process is the exact same as your Suburban.

expert reply by: Samuel C

0

Tony

3/20/2025

I think the issue is... As I've seen in my Toyota Tacoma. When the brake pedal is pressed 12V comes through the switch when it is released the cold side goes to ground. I haven't been able to find it again but I remember reading that this grounding will kill a Tekonsha break controller. I thought maybe I could put a diode in there to prevent the controller brake wire from going to ground....

Reply

Jameson C.

3/20/2025

@Tony That type of grounding shouldn't affect a Tekonsha brake controller but we do have a one way diode you could use with the part # RM-690 if you wanted to be extra cautious.

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Should Stop Light Switch Wire On Trailer Brake Controller Have Ground Or Power?

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