Coolant Temperature Sensor / Switch HVAC: Description and Operation

Coolant Temperature Switch Circuit (A/C Only):

The Coolant Temperature Switch, located in the thermostat housing, is a contact type switch. It is normally in the closed position allowing current flow. When the engine coolant temperature is 233 - 244° F (112 - 118° C) the switch will open cutting power to the ECU, and helping to prevent engine overheating.