Troubleshooting One Brake Locked Up on Trailer

Updated 09/03/2025 | Published 06/08/2015

Question:

Trailer fine last year. First trip this year 1 of 4 brakes locked solid. Felt a lot of resistance on way to campground. Smoked from site to dump station. Locked solid when leaving dump station. Trailer unhooked from truck controller is Tekonsha P2 - purchased from you. Lifted drivers side of trailer and verified wheel still locked while the other wheel turned freely. Could not even get adjuster to move brute force and ugliness removed drum. Put drum back on and rotated in direction of travel. Result - I could hear the magnet dragging in the drum and felt the rotation getting tighter in spite of the adjuster being backed all the way down. Did not do any electrical test.

asked by: Richard B

Expert Reply:

Sounds like there could be a short in your trailer wiring for one of the brakes or there could have been a mechanical failure in that one brake assembly. The second possibility is more likely since only one brake was affected.

First inspect the wiring to the affected brake (and the others too) to check for signs of damaged wires or worn insulation that could cause a short. If the short was near the one brake assembly then that might cause the issue to be isolated to the one brake. Also check the trailer and vehicle connectors for signs of corrosion.

You'll also want to inspect your bearings and the drum surface for any signs of mechanical damage. It is possible a foreign object found its way into the brake, or that a spring or other mechanical component has failed. Check the bearings for damage from heat - look for any obvious damage as well as to discoloration from excessive heat and replace components as needed.

You can also test the affected brake by applying 12V power directly to its wire leads to see if it engages and releases properly. The brake magnet itself can also be tested for proper operation by following the procedure noted in the linked article.

expert reply by: Chris O