Just done some testing with an LED and two wires. Ignition power seems to be top left as you look at the face of the plug, Earth seems to be the bottom right, and the light feed seems to be one in from right on the top. The fan came on a couple of times when I was playing with it, I'd hazard a guess that it was bridging top left and bottom left, with the earth connected via the LED. I could be ass-backwards wrong on that though. Might give you a steer, but bare in mind that Im literally basing this off whether a light bulb comes on or not. Edit: I've got about 45 minutes before I need to get ready for work so if you want anything testing etc in that time, I'll do what I can.