Trailer Brake Controller Randomly Applies Trailer Brakes
Published 11/03/2014
Question:
My trailer brake is engaging ad-hoc when Im not depressing the truck break. The trailer break controller lights starts to blink and theres a back and forth motion as im applying the gas but the break is being inacted at the same time. Doesw not happen all the time but ad-hoc but indeed very worrisome.
asked by: Gary
Expert Reply:
The erratic behavior of your brake controller could be caused by several different factors. The first thing you will want to do is test the brake controller to determine if it is the problem. You will need a circuit tester if you do not already have one, # PTW2992.
In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use your tester to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override or brake pedal. If it shows power at idle then there is something wrong with the controller and it will need to be replaced.
If it tests fine then reconnect the blue wire. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.
You can test the brake output pin and it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to track down.
If the truck side checks out fine then it could be the wiring to the brake magnets or the magnets themselves. Inspect the power wires to the magnets and look for pinched, frayed, or damaged wires and fix as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces.
You can visually inspect the magnets and if you can see the copper windings coming through the magnets will need to be replaced. To further test the magnets you can follow the help article I have linked. I have also included some help articles on testing and troubleshooting brake controllers for you.
