Tekonsha P2 Trailer Brake Controller Showing SH at Idle but Not When Stepping on Brakes

Question:

My prodigy shows S.H. - indicating a short on the brake wire at idle. Pressing the brake then shows the proper number and the brakes do engage. Further, if I, using aligator clips, connect just the brake lead and just the ground lead - the device works normally. In addition, when I use a multi-meter to check the wiring, I do get a short checking the blue wire on the plug and ground. looking for some hlep - thanks.

asked by: Vittorio B

Expert Reply:

It is possible that your brake controller is showing SH if there is corrosion in or behind the 7-Way trailer connectors, truck and/or trailer side. If you do not see corrosion in the plug faces, it could be built up in the back where the wires attach. This may bee causing the problem.

If you cut the blue wire from the back of the controller and test it there while applying the manual override and everything works properly and there are no error messages, then that would indicate a short somewhere in the wiring system and not a problem with the controller itself.

Make sure to check all the wiring and ground connections starting with the brake controller where it is wired into the truck, then move back from there to check the 7-way wiring on the truck including making sure the ground wire is attached to a clean metal surface, and finally do the same on the trailer wiring.

If everything comes up as being intact and you cannot find any wiring errors yet the controller is still showing a fault, it may be the brake magnets on the trailer (if the issue happens with a trailer connected). You would need to first check the brake magnet wiring for proper grounds and intact wiring.

Then you can visually inspect the magnets. If the windings are coming through they will need to be replaced. Finally, you can check the magnets with your multimeter. I have included a link to an FAQ that explains how to check the magnets.

expert reply by: Michael H