Troubleshooting Brake Controller that Only Works With Manual Override


Hi, I have a really old Kelsey trailer brake controller Not even sure what model. It’s on a 99 f250 superduty. Trailer brakes don’t work when brake is pressed only when manual overide is pressed. When I test the blue wire Coming out of it when brake pedal is pressed, the tester light is very dim. When I apply manual overide button, light is bright. I cut blue wire 6” from controller and tested it when manual overide is pressed and light is bright. So seems like controller is still good, but maybe not? Any help would be appreciated! Thanks,


Expert Reply:

Did you check to make sure the red wire of your controller has 12 volts when the brakes are applied? That's the circuit that would be at fault if the controller itself is still good. I'd verify that you have 12 volts on the red wire of the controller with a circuit tester like part # PTW2993 and if it does then the controller is faulty. If not, then the wiring for that circuit is bad. You'd need to check the condition of the connection for the red wire and then also check the fuse for the third brake light of your truck as well.

For a brake controller replacement I would recommend the Prodigy P3 Brake Controller part # 90195. This is our best selling brake controller because of how well it works and how easy it is to setup. This is a proportional brake controller that senses the amount of braking the tow vehicle is applying and applies a proportionate amount to the trailer brakes. This will be the last brake controller you buy. It can easily be transferred to future vehicles as well.

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expert reply by:
Jameson C

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