Operation CHARM: Car repair manuals for everyone.

Thermostat, Engine Cooling

If the thermostat opening voltage is greater than 0.75 volt and less than 78°C (173°F), install a new thermostat.
If the thermostat opening voltage is less than 0.75 volt and greater than 78°C (173°F), the thermostat is good and a new thermostat is not required.