Someone sent me one of these switches, much better switching temps, the one I tested came on(closed contacts) at 92C, and off at 88C.
My fan is set to come on at 95C and go off at 92C, so it cycles all the time.
Using deflectors around rad/cooler to stop air spill helps a lot, especially the amount that pushes downwards to avoid going through the rad, air will take the easiest route.
tabetha