Troubleshooting Trailer Brakes that Lock Up from Brake Controller  

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Expert Reply:

There could be a lot of reasons the trailer brakes are locking up. First, take a look at the controller. If it is a proportional controller and it has been bumped out of the proper alignment (such as tilted to far up or down, side to side, or turned left or right) that can affect the way it functions. Make sure to check the instructions for how the controller needs to be mounted.

To test the brake controller further you will need a circuit tester like # PTW2993. Sever the blue wire a few inches back for the back of the controller. Then use the circuit tester on the end of the blue wire coming out of the controller. It should only show power when the manual override is applied. If it shows power at any other time then the controller is bad and will need to be replaced.

If the controller checks out and it is mounted properly, reconnect the blue wire. Next, fully apply the manual override and let it snap back into place. Do this several times to clean the internal contacts of the controller. Dirty contacts can occur if the controller has not been used in a while and that can affect performance.

Next you can check the trailer and vehicle side connectors for dirt and corrosion. Dirt and corrosion can build up on the pins and inside the connectors where the wires attach. This can cause a short circuit and can make the brakes apply too aggressively.

You can also check the brake magnet wiring and the brakes themselves. Look for any nicked wires that may be touching bare metal. Make sure the ground wires from the magnets are attached to clean and corrosion free bare metal surfaces. Check the brake adjustment as well. You should be able to turn the drum by hand and hear a slight but constant drag of the pads on the inside of the drum. Adjust accordingly.

Also check the magnets. If you can see the windings coming through then the magnets will have to be replaced. To further test the magnets I have included a link to an FAQ you can follow. I have also linked an FAQ on troubleshooting brake controllers for you.

expert reply by: Jameson C

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