Installation of Brake Controller on a 1996 GMC with Brake Lead Hot All The Time At The Trailer

Expert Reply:

Most likely you have the red wire going from the brake switch to the brake controller hooked up to the wrong circuit. Use a circuit tester, item # 3808 if you need one, to find the wire coming out of the back of the brake pedal switch under the dash that is hot (12 volts) when the brake is applied and cold (no power) when the brake pedal is not applied. Another possibility is that you have the wire coming from the battery or fuse block to power trailer accessories hooked to the wrong terminal in the trailer connector. If this is the case you will need to rewire the connector using a circuit tester to be sure the wiring is wired the same for the vehicle and trailer.

expert reply by: Bob G