Troubleshooting Brake Controller With Blinking S.H Display  

Question:

Expert Reply:

The display S.H indicates a short in the system and can cause a number of issues. You will want to do some testing of the brake controller to make sure it is working properly.

In the truck cab you will need to cut 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 show 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 checks out okay, then reconnect the blue wire. You will then need to move on to the truck side trailer connector. Dirt or corrosion can cause a short in a trailer connector. Check the truck and the trailer side connectors to make sure they are clean and free of corrosion inside and out, and clean as needed.

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.

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 broken, pinched, or damaged wires and repair as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces.

You can inspect the magnets and if you can see the copper windings coming through, the magnets will need to be replaced. To do more testing of the magnets you can check out the attached help article. I have also included links to some help articles on testing and troubleshooting brake controllers you can take a look at.

expert reply by: Jeffrey L

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