NC Code Pops Up on Tekonsha Primus Brake Controller While Towing a Trailer

Question:

My brake box usually shows c when im driving but sometime it flashes nc. I do have brake so im not sure if its a lose connection. is the plug moving around when im driving so it not always getting a secured connection

asked by: Amber

Expert Reply:

On the Primus brake controller # TK90160 the c indicates that a trailer is connected and nc means that a trailer is not connected. If you have a trailer connected and see nc then the most likely issue is a dirty or corroded trailer connector that is not getting and maintaining a good connection.

Make sure that the vehicle and trailer side connectors are clean and free of corrosion on the inside where the wires attach and on the outside on the pins. this is also a good time to check for loose connections and fix as needed.

If you continue to have problems, then there are some tests you can perform to determine if the brake controller or something else is the problem. In the truck cab you will need to 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.

If it tests fine then reconnect the blue wire. Then move on to the truck side trailer connector. 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.