i have tried wiring my fan through the thermo switch but could not get it to work. It works ok when wired through a toggle switch though. at what temperature should the thermo switch cut in and do i wire the live feed to it and from there on to the fan.

Usually goes...
fused+ to switch
switch to fan
fan to earth.

Switch should have 2 numbers on it for temp it comes on and off, ie. 100/95 would be on at 100'c, off at 95'c.

adrian

Careful with the load on the thermo switch - use a relay if in doubt or it will just go pop.

If you are using a Yamaha radiator fan switch, then the temp it switches on at should be 105 +-1Deg C and switch off at 99 Deg C. If you want to test it, place it in some oil and rause the temp on a cooker. Don't use water as it will boil at 100 deg C and it will never switch on. When it is working inside the radiator, the boiling point of water is around 125 deg C if you use a 1 bar cap.