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

Expert Reply:

If the problem is that the brakes on the trailer are constantly engaged, 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.

If you are maybe asking whether you will get a power reading at the vehicle plug in the rear of the truck, the answer would be yes. With the power wire for the vehicle plug hooked up to the vehicle battery, you will read power on this port at all times. If your trailer has an accessory that will cause a draw at the vehicle plug, such as a breakaway kit, you would need to disconnect the trailer from the truck when not towing or parking overnight, etc.

expert reply by: Bob G