I have never seen my radiator cooling fan turn! I have let the temp climb to around 90-95 and it doesn't cut in, I (obviously) don't want to let it go any higher, so I switch off. However, when at normal temp, I crank the A/C on full and the fan works, not as fast as I would expect, but it runs. There is no binding from the fan and it rotates smoothly. Do I have a problem and if so, what should I be checking?