Troubleshooting Why Trailer Brakes Lock Up While Driving  

Question:

Expert Reply:

If you have electric brakes, there could be several reasons why they are locking up while you are driving. There could be a malfunction inside the brake controller, a problem with a ground, a short in the wiring, or a problem with the magnets.

To test the brake controller, sever the blue wire a few inches from the back of the controller. Use a circuit tester like # PTW2993 if needed to test the blue wire on the brake controller side. Fully apply the manual override and the blue wire should show a signal on the tester. Let off the manual override and the wire should show no power on the tester.

If there is no power when you apply the manual override or there is power when you let off of it, that indicates a problem with the brake controller and it will need to be replaced. While you are testing the brake controller, you can also check to see if it is mounted within the limits in the instructions.

If you have a proportional controller, they have to be mounted in the direction of travel, cannot be tilted or turned side to side, and usually have to stay within a certain range pointed nose up or down. If that is off, it can cause the brake controller to perform erratically.

If you determine that the brake controller is sending the right signals along the blue wire and it is mounted correctly. Next try fully engaging the manual override and then let it snap back into place several times. This will clean the contacts inside the controller.

The next wire you can check is the red wire on the brake controller. Use the tester to verify that the red wire only shows power when the brake pedal is pressed and not when the head lights or turn signals are on. If you find it is connected to the wrong wire, use the circuit tester to find the correct wire on the brake switch.

Once you have finished with the brake controller, go back to the trailer connector on the tow vehicle and check for dirt and corrosion in the connector and in the back where the wires attach. Do the same for the trailer side connector. Dirt and corrosion can cause a short on the brake wire.

Next check the main ground on the vehicle and trailer sides ad at the brake magnets. They should all be attached to clean and corrosion free bare metal surfaces. Check the power wires going to the brake magnets. Look for any nicks in the wires where there may be exposed wires touching the metal of the trailer frame.

You can then inspect the trailer magnets. If you see the windings coming through then the magnets need to be replaced. To further test the magnets, I have included a link to an FAQ article that will explain the process. Once you have found and repaired the issue, I recommend resetting the brake controller according to the instructions as if it were the first time you were using it.

If the trailer has a breakaway system, check the system battery and wiring as well and make sure the pin on the breakaway switch is fully inserted.

If you have hydraulic brakes there may be air in the lines or a bad wheel cylinder. You can have the trailer breaks bled and check for leaks at the wheels and fix as needed.

expert reply by: Michael H

0

Dan

4/23/2024

One of my electric brakes on my trailer locks up when i apply my brakes it has 4 wheel brakes i have replaced the backing plate and the drum any suggestions ?

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