Primus Trailer Brake Controller Shows NC with Trailer Connected and No Power Output on Display

Question:

have had unit installed and working for years . n c comes on sometimes and when trailer is hooked up the red dot comes on but no numbers come on when applying break and manual button is pushed still the brakes do not work

asked by: Dana W

Expert Reply:

It sounds like there is possibly more than one issue causing your brake controller to not work properly. First, the easiest thing to check would be the truck and trailer side connectors. Make sure they are clean and free of corrosion inside and out. You will also want to check for loose wires or exposed strands touching bare metal along the wiring to the connectors.

To test the brake controller, the first thing to do is sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle, then there is something wrong with the controller and it will need to be replaced.

It could also 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.

expert reply by: Michael H