[DonSor]

First of all you have a temperature switch instead of a guage. The switch does not tell you what the coolant temperature is, only a range so that if the coolant goes beyond a certain range of temperature it indicates too hot or too cold. To check if the temperature switch is OK, disconnect the wire and turn your ignition on (w/o the engine running). Your gauge should read peg max. Then short the guage wire to ground and it should read minimum. Assuming that your engine reaches operating temperature turn your heater on, blower on high and feel the supply and return hoses to your heater coil. There should be a noticeable difference in temperature. What you find from that is whether your heater valve works or not. Finally, move your heat/cool selector level and see if you are getting any vent changes. This to test if the louvre/s are moving to the right position. BTW what caused the stat to be in four pieces?