Why is my temp gauge rising and falling??
 

On my '93 325i, I noticed my normally stable temp gauge rising and falling during constant driving or even when idle. It goes from normal(middle) up to the red mark then will go back down over a couple of minutes or less. No boil-off(loss of coolant) and it does not seem to be over-heating but I did find my elec. fan not coming on at any time. New metal water pump and belts. Engine clutch fan working.

Check my fuses and relays which are all operating. At the fan I did not find any voltage when the engine was hot and I thought I should have voltage on the pin to the fan. So at the radiator switch, how can I check it before I buy a replacement and try it.

Thanks,