Troubleshooting Brake Controller Install Where Brake Lights Apply with Manual Override

Question:

I have a 2008 Ford F250 with a Curt Discovery trailer brake controller. When using the squeeze box it does not activate the trailer brakes, trailer brake lights, truck brake lights, or kill the cruise control on the truck. I have checked my grounds at the plug and at the controller and both have stable grounds. All running lights work on trailer as well as brake lights, truck brake lights, and cruise control kill. I have a constant 12 volts to trailer brakes at the plug and at the blue wire on the back of the controller. I replaced it with a Tekonsha and I have the exact same issues. Trailer hooked up to dads f250 works flawlessly so I know the issue is on my end.

asked by: Houston M

Expert Reply:

The problem you are having is the circuit that the red wire of your brake controllers is attached to. It sounds like the output wire (blue wire) may be shorting out to the stoplight circuit of your truck and is applying voltage to your brake light circuits which is causing them to illuminate.

Basically you need to clean up the wiring of the brake controller so that it will work properly. Black wire needs a clean connection to 12 volts, white needs to ground, blue needs to be brake output, and red needs to be to a circuit that only sees voltage when the brakes are applied.

expert reply by: Jameson C