Trailer Brakes Intermittently Turn On While Driving without Using Brake Pedal or Manual Override

Published 03/13/2014

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Question:

The problem I am having is the trailer brakes will intermittently kick in while driving. I had a trailer shop look at it but they didnt find anything. Can you give me an idea of what could be the problem?

asked by: Lisa

Helpful Expert Reply:

It is possible that there is a short somewhere that is intermittently kicking in due to vehicle/trailer position changes as you drive. The likely culprits are the trailer connectors on the vehicle and trailer. You will need to make sure that the connectors are clean and free of corrosion inside and out.

To test the controller use a circuit tester such as # PTW2991. Sever the blue wire a few inches from the back of the controller and test the end coming out of the controller while fully applying the manual override. The controller should only show power when the manual override is pressed. Power at any other times indicates a problem inside the controller and it will need to be replaced.

You will also want to check the red wire connection on the controller. It should only have power when you step on the brake pedal. If it shows power at any other time then you are likely connected to the wrong wire.

If the brake controller checks out fine then reconnect all the wires. Then check the brake output blue wire from the controller to the connector looking for any loose or frayed wires and fix as needed.

On the trailer side you will want to inspect the brake magnet wiring the same way. Make sure the grounds are connected to clean and corrosion free bare metal surfaces. Then visually inspect the magnets and if you can see the windings coming through they will need to be replaced.

To further test the magnets you can follow the how-to article I have linked. I have also linked a couple on brake controllers for you.

expert reply by: Michael H