Troubleshooting Brake Lights Always on After Installing a Brake Controller

Updated 06/23/2025 | Published 06/18/2025

Question:

Good evening, I purchased a C51170 Curt Spectrum Trailer Brake Controller - Dash Mounted Knob - Up to 4 Axles - Proportional. I installed on a 2019 Nexus Wraith RVInternational Durastar 4300. I followed the Manufactory manual for the truck and found the 4 wires ready to plug and play on the brake controller. However the brake lights are continuously on. Im going to test the red wire from the truck for a possible continuous power situation from the brake pedal. I find it rare as the wires are supposed to have been left pre done from the factory. Please any advice will be greatly appreciated.

asked by: Honori

Expert Reply:

Hey Honori, welcome back. The red wire being the wrong one would cause that issue if it was wired incorrectly but it would also leave your trailer brakes activated. I don't think it's that.

It sounds to me like you have a short or fault somewhere in your tow wiring. Did you have any issues with your trailer lights before you installed the brake controller? If you don't know do you have another vehicle you can connect your trailer to? Isolating the problem to the trailer or vehicle is going to save you some steps.

I recommend checking the connectors from your motorhome and trailer. Make sure that they are clean and free of debris. If they check out you will want to move on to your grounds. They need to be securely connected to a clean, bare-metal surface free of paint, debris, or corrosion. If one of these steps doesn't fix your issue you'll need to go through your trailer's wiring and see if there's a mis-wire or frayed one somewhere that's drawing power.

expert reply by: Jerred H

Honori

6/23/2025

I tested all on Saturday with a test and my red wire is actually for power not brake light. I re did the connection and everything works great! Thanks