Trailer Brakes Lock Up When Connected and Display Shows Nothing on Reese Pilot Brake Controller

Expert Reply:

It sounds like you have an open circuit on the brake output wire to the trailer brakes. This means that the brake circuit is receiving constant power and that is locking up the trailer brakes.

First, you can test to see if the blue wire on the brake controller is sending power back. Sever the blue wire behind the controller leaving enough to reconnect when finished testing. Use a circuit tester like # 3808 if needed to test the blue wire. It should only show a signal when the manual override is being applied. If it shows a signal at any other time, the brake controller is bad and it will need to be replaced.

If the brake controller checks out then move on to the trailer connector on the vehicle. If there is dirt or corrosion in the connector or behind it where the wires connect, that can be causing a short circuit. Also check the trailer side connector.

Use the circuit tester to test the functions on your 7-Way connector pins and make sure the 12 volt output is in the 1 oclock position and the brake output pin is in the 5 oclock position. Then, make sure that the trailer side connector is pinned in such a way to accept the way the vehicle side connector is oriented.

If all of that checks out, make sure that the main ground on the trailer is attached to a clean and corrosion free bare metal surface. Check the wiring going to the brake magnets for nicks or breaks and also check the brake magnet grounds.

Finally, you can test the magnets themselves. Start with a visual inspection. If the windings are coming through, then the magnets will need to be replaced. You can further test the magnets by following the FAQ article I have linked for you.

expert reply by: Michael H