Intermittent Trailer Brakes


So, while driving through the mountains of New Mexico and Colorado my truck kept giving trailer brake errors. First, “Check Trailer Brake Wiring” and then “Trailer Brakes Disconnected” and finally the red light indicating no trailer brakes. There was no pattern just completely random alarms, but when it said “disconnected” there were NO trailer brakes. Fortunately having a 4WD truck with 4-wheel Low helped maintain control over the passes.

Finally back home, and a quick Internet search seemed to indicate that the wires running through the axels were at fault. Seemed a bit sketchy, but when pursuing this potential issue I discovered that the front axel wire had worn through the outer jacket and a red wire was exposed. Then, the rear axel wire had not only worn through the outer jacket, but the red wire insulation as well – exposing bare copper wire to the inside of the axel and grounding out the brakes.


Internet articles recommended running 12-gauge wire but after seeing that everything else was 16-gauge, it seemed to me to be ok to run a 14-gauge jacketed pair across the back of the axel. This would leave it exposed for future inspection and easy repair should that need to be done.I did trace out the wiring from the plug and color-coded the existing wiring with electrical tape at the brakes according to the standard for brake wiring (Blue=Voltage, White=Ground). Of course, the brake magnets could care less about polarity but I thought this might be useful if in the future I needed to revisit the brake wiring. As you can also see the jacket twin wire runs across the rear of each axel and is cable-tied to keep it in place.

-Bob Tassan