I am wiring a brake controller for my trailer brakes. It instructed me to connect to the cold side of the brake switch, which I interpreted to mean 12 volts when the brakes are on. One of the four wires did indeed give 12 volts when the brakes/ignition were on so I chose that one. Driving around tonight my brake controller randomly came on as if I were hitting the brakes when I actually wasn't. Additionally I can hear a factory relay under the dash clicking when I hit the override braking button on my controller (which shouldn't be happening).

Has anyone hooked up a brake controller and if so which wire did you use?

Thanks

 

I recently put a Tekonsha P3 in my Disco. I connected Red controller wire to the Green/Purple brake wire.
This is for my Disco
Vehicle side of 7Pin Trailer Socket: (second colour is trace)
Black - Ground
Red/Orange - RH Tail
Green/Purple - Stop Lights
Green/White - RH Indicator
Green/Red - LH Indicator
Red/Yellow - Rear Fog
Red/Black - LH Tail

Single Pin Socket A:
Green/Brown - Reversing light

Single Pin Socket B: 20A fuse F6 in Satellite 2 (I think)
Purple/Brown - Power