2nd Gen Non-Engine/Transmission Brake Light & Brake Controller Wiring Question

[TinCanTourist]

While out running errands today I noticed that my brake lights were staying on with the engine off. Checked the peddle switch to see if it was sticking, didn't appear so, then pulled the 20A brake light fuse in the main panel under the hood, still staying on. One would think pulling this fuse would shut the brake lights off. A little further investigation and disconnecting the brake controller from the quick disconnect seemed to solve my immediate problem of getting the lights to turn off.



Why would the brake lights stay on if there was no fuse in the circuit? Also, is there a test procedure for checking the brake controller circuit to the quick disconnect before I pop for a new one (DrawTite ActivatorII)?

 

[Wiredawg]

Just a guess, but you can have voltage on the circuit with the fuse out if the voltage is being introduced from another source... a cross between the brake controller circuit and the brake light circuit. The controller could be bad and is backfeeding it though the truck's brake light switch. You can test it by connecting the controller back up and isolate brake controller lead that connects to the brake light switch. If you read voltage with a multi-meter or light tester, the brake controller is bad. Confirm the results with the controller manufacturer.



Hope this helps,



Wiredawg

 

[TinCanTourist]

Thanks, Wiredawg, I'll drag out the multi meter and see if I get voltage at the brake switch.

 

[DieselDoghouse]

What wiredawg said. If you do have a phantom circuit you might be able to add a diode to prevent backfeeding of voltage (or the controller had one and its bad now!!!)

 

[SSolderitch]

controller test outside truck. apply power & ground to correct wires, add a 12v stop bulb on the blue wire and then to ground. should be off. with manual override bulb should start out dim and go to bright as you slide... . when you trigger the unit with the brake switch wire - bulb should go full bright and off when wire removed.

 

[TinCanTourist]

Thanks guys, I'll test the system this weekend. I suspect that the controller is going bad (wanted a new progressive type anyway). Won't have to tow until after the first of the year so I have time to reconfigure some components, like an exhaust brake and new controller.