Troubleshooting Smoking Brakes After Brake Controller Installation

Updated 12/22/2025 | Published 10/28/2024

Question:

I have a 2017 Forest River Salem Cruise Lite I have never pulled a trailer with brakes before now. I wired in a Reese trailer brake control into my 2009 GMC Serria 1500, and went for a test drive. I thought everything was fine but when I got out the brakes were smoking. I cooled them off with cold water and now every time I touch my brakes the controller says OL, overload. What did I ruin?

asked by: Blayne

Expert Reply:

Hi Blayne; I'm not sure which brake controller you have but the OL code typically indicates the brake circuit is drawing too much current and there may be a short. Since your brakes were smoking it sounds like they were engaged the entire time which means you had constant power on the brake output circuit.

With a new installation I expect you might have mixed up some wires. Go ahead and double check to make sure the white wire is hooked to the ground, red to the stoplight switch, black to 12V power and blue runs to your brake output headed back to the 7-way. You can also test the wires running out of the brake controller to make sure you don't have constant power on the blue wire. If you do, it could be an internal issue with the brake controller.

If all of that checks out go ahead and check the 7-way on your truck. If you have power on the brake output pin it could be corrosion allowing 12V power to cross over or you have a short somewhere in the wiring. Trace and repair as necessary. If everything checks out on the vehicle side I would check the trailer side connector and with it plugged in work your way back with a tester until you find where the power is coming from on the brake output wire.

expert reply by: Robin H

Robin H.

12/22/2025

Hey Blayne, what ended up happening after you checked the wiring on your Sierra and trailer brake controller? Were you able to track down the short or constant power on the blue wire? Sharing what fixed it could really help others running into the same overload issue.