Troubleshooting Trailer Brakes that Hum But Do Not Lock Up

Published 11/16/2018

Question:

Trailer brakes humm but dont lock on hard

asked by: Keith W

Expert Reply:

The humming sound you hear from your trailer's electric drum brakes is a good sign. It means that the brakes' magnets are being energized by the output from the trailer brake controller in the vehicle. Most likely your brakes aren't adjusted properly and that's why they aren't grabbing like they should.

When a drum brake is adjusted correctly there will be slight drag on the drum when you rotate it by hand. You should be able to hear and feel this drag. Try adjusting your brakes so that they drag slightly on the drum and then test the trailer with your vehicle.

We have a video that shows how to adjust the brakes, see link. At the 4 minute and 30 second mark you will see the adjustment procedure.

expert reply by: Jameson C