Trailer Brakes Fail When Brakes are Applied Over 5mph With a New Brake Controller and Wiring Harness

Question:

When brake is applied over 5mph it senses output shortage and overload on brakes then shows no brakes on Prodigy P3. It works great in reverse or sitting still but then quits when brake pedal is applied driving forward. All pins on harness show correct and all lights work correctly. New controller, new harness and new OEM truck connector.

asked by: MATT G

Expert Reply:

If you are getting power to the 5 o'clock pin on the 7-Way connector for your truck (which is for the brake controller), then the problem is most likely with the wiring on your trailer. If you have access to another vehicle with a 7-Way wiring harness, I recommend hooking that up to the trailer as well just to verify. If the trailer works just fine with a different vehicle, then there is an issue with the wiring on your truck. You will have to press the manual override lever on your Prodigy P3 # 90195 when testing the 7-Way.

Either way, what you will want to look for is any wiring that might be corroded, bent, or exposed. You will also want to check to make sure that your ground wire is secure and doesn't have any corrosion either. If you find some faulty looking wiring, then you can replace it with 10 Gauge Wire # 10-1-1 and Butt Connectors # DW05745-5.

If you don't see any faulty looking wiring, then I recommend hooking the trailer up to a battery and using a Circuit Tester # PTW2993 to test the wiring along the trailer to see where the bad section of wiring is.

If all of the wiring looks good on your truck and trailer, then I recommend taking your setup to a professional mechanic who can better diagnose the problem since they can physically inspect it.