some of which are even variable, none of them are capable of switching two fans and they rarely seem to last longer than a few months due to corrosion or water ingress.

Many use a mercury bulb on the end of a copper capilliary tube which needs to be inserted inbetween the top hose and the pipe which comes out of the radiator - it is near impossible to seal this joint and the thin capilliary tube is fragile.

Probably the best testamonial for this kind of switch is that it is used by almost all motor manufacturers to switch electric fans.

We stock the following four kits. It's easier to see what they contain from a picture.