Brake Controller 5100 Wire that Does Not Have Voltage Until Brake is Pressed

Expert Reply:

I am sorry you are having a problem with your brake controller wiring. My initial reaction is that there is a ground issue from the odd readings you are getting from the wires under the dash. Start with no trailer attached. Make sure that all of the grounds you have hooked up are solid and clean. If that does not work, then I would go to the connection right at the brake pedal and test the wires coming out there. One of these wires should provide no voltage until the brake is pressed and then voltage should register. The standard brake wire for Chevrolet is light blue but that does not mean that this model is not different. Sometimes you just need to back up and go over everything to make sure something didn't get crossed up in the process. I think you are right that the black wire is ground and the orange wire should be power but should be 12 volts plus. The yellow wire may be going to the third bake light causing the voltage problem, so there is another wire you may be missing. I can't help but think there is a light blue wire there somewhere (especially after looking at the picture of part number 5100). A final thought, check all of your taillights, even the third brake light. If one of those is out, that could possibly be the problem. I hope something here helps, it is hard to diagnose at a distance but let me know if you don't get it working and I'll do the best I can to help. You are almost there.

expert reply by: Bob G