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Troubleshooting P3 Brake Controller that Applies Light Braking All the Time  


I have tried several test to find out why my electric brakes are not working. First I have tried 3 different trailers , one with single axle and the other have two. with the same out come. I can hear a slight noise from the brakes and a light braking. My Tekonsha Prodigy P3 shows voltage of over 10v going to the brakes. I have checked and added extra ground wires. I have checked the brake voltage on the trailer and it matches the P3. The P3 shows 11amps going to the brakes on the double axle and 5amps to the single. I just did a 10k mile trip and it work all the time. This just started a couple of weeks ago. Any idea?


Expert Reply:

Sometimes brake controllers need a hard reset to clear out internal issues. Even the very reliable P3 part # 90195 can need this occasionally so I'd try unplugging it for a few seconds to let it reset and plug it back in. Hopefully that fixes it but not here are steps to troubleshoot and determine exact location of the problem.

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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