Prodigy Brake Controller Flashes SH After Moving it from One Car to Another

Published 01/12/2015

Question:

HI, I HAVE RE-INSTALLED THIS UNIT FROM MY OLD CAR TO THE NEW ONE. CONNECTED THE WHITE WIRE TO EARTH, BLACK WIRE TO CIRCUIT BREAKER THEN POSITIVE, BLUE WIRE TO TRAILER PLUG, RED WIRE TO COLD BRAKE LIGHT SWITCH AND IT KEEPS FLASHING SH CONSTANTLY, CANT UNDERSTAND WHY, WORKED PERFECTLY IN THE OLD CAR. COULD IT BE A FAILER IN THE CIRCUIT BREAKER? HELP

asked by: WAYNE

Expert Reply:

The circuit breaker would reset so the power would be interrupted, and you wouldn't see a display during that time, so I don't think it is the circuit breaker. The white ground wire, if hardwiring in the controller, should go to the negative battery terminal. It needs a substantial ground and that is the best place to get it. The SH is indicating a short circuit

It could be the red wire. On a brake switch there can be more than 1 wire that shows power with the brake pedal. If the wire shows power with the headlights or turn signals on then it is not the correct wire.

You can test the controller to determine if something happened to it during the removal or re-installation process. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle then there is something wrong with the controller and it will need to be replaced.

If it tests fine then reconnect the blue wire. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.

You can test the brake output pin and it should only show power with the manual override. If it shows power any other time, then there is a short somewhere between the connector and the brake controller you will need to track down.

If the truck side checks out fine, then it could be the wiring to the brake magnets or the magnets themselves. Inspect the power wires to the magnets and look for pinched, frayed, or damaged wires and fix as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces. I have linked some help articles for you as well.

expert reply by: Michael H