Mine being an ex police, I just used one of the switches on the right hand cluster. The fan switch switches to earth so all I did was run a lead from the fan wire on the radiator thru the switch, to earth. I have replced the switch in the radiator 3 times and still cannot get it to last more than a couple of months before it doesn't work and the guage gets very close to the red! Did it too long age to remember which wires from the switch block I used, just needs to be an independant switch without a common feed.
