Probably a 195 (F) degree thermostat. That would be what the system is designed for.
The thermostat is stuck open.
It should have a 195 degree thermostat.
Whatever the thermostat is preset to, probably 195 degrees F.
The factory thermostat, made by Stant, is 195 degrees Fahrenheit.
Chevy Cavalier should run about 195F or 91C
220.
Take a look where the lower radiator hose connects to the engine. Where the hose connects, you should find the thermostat.
Remove the water supply hose from the top of your 2003 Chevy Monte Carlo thermostat housing. Remove the thermostat housing retaining bolts. Lift the old thermostat out. Drop the new thermostat in and reverse the process.
The thermostat should be on the top of the engine under the water inlet. Drain the radiator. Remove the top radiator hose from the inlet. Unbolt the inlet, and pull the thermostat out for replacement.
Behind the lower radiator hose
location for 2003 chevy trailblazer coolant temperature sensor
Well knowing these trucks as I do you must determine if it is really the temperature sensor that is gone out or if it is the thermostat, water pump, fan clutch or stepper motor in the cluster.