Troubleshooting a Brake Controller that is Sending Max Voltage on Brake Output Circuit


I own and have been successfully using the Hayes Genesis model 81790 for the past two years. recently after a long rest I hooked up the horse trailer to my F250 Ford truck and the brake controller defaults to 99 braking power. After consulting to instructions I successfully reduced the minimum power set to 5 and the maximum setting to 25 with no change. Your ops manual says that the possible solutions listed for problems with brakes locking up are either minimum and maximum power settings or Faulty break away switch. the switch is not powered by a separate battery so is non operational. Any ideas as to what could be making the brakes lock up?


Expert Reply:

Sounds like you need to test the brake controller so we can narrow down where the problem is.

Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # PTW2993, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.

I am including a link to a video that will show you how to test the wiring on a brake controller.

expert reply by:
Jameson C

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