We've tried many different fan thermo switches in the Interceptor. Due to a high percentage of failures on the original for the Mk3 and other aftermarket switches, we're really liking this guy! We now offer a kit incorporating the screw-in type like on the Mk1s & 2s with an adapter piece so you can install it on your Mk3. This switch comes on at about 82 degrees C or 180 degrees F which is the same temp that your thermostat should open.  This switch shuts off at 77 degrees C or about 171 degrees F.   This is all we will use or sell. If your radiator is out, this can be soldered on for a permanent fit. Those 3 studs have a tendency to break off when you least want them to!