Troubleshooting Trailer Brakes Locking Up When Truck is Started

Question:

the trailer brakes work just fine if the truck is in acc. mode, but once it is started they lock up

asked by: Kevin

Expert Reply:

It sounds like you might have the red wire (brake input) on the brake controller connected to the wrong side of the brake switch wire on your vehicle. The first thing I recommend doing is verifying that the red wire from the controller is spliced into the wire behind the truck's brake pedal that ONLY receives power when the brake pedal is depressed, and no power with any other function.

I recommend using a circuit tester like # PTW2993 to make sure you have the right wire.

If this does not resolve the issue, then you will want to inspect both the truck and trailer side 7-Way connector. Check for corrosion or debris that might be built up around the pins, cleaning out as needed. It could be that corrosion has bridged a couple pins together and is causing a short.

If the brakes still lock up as soon as you turn the truck on please let me know and we can continue to troubleshoot.

expert reply by: Chris R