Coolant Temperature Sensor / Switch HVAC: Description and Operation

Engine Coolant Temperature Switch Location:

The coolant temperature switch, mounted in the thermostat housing, allows the "A/C ON" signal to be transmitted to the ECU.

Air Conditioning Switch And Relay Circuit:

When the engine coolant temperature is below 239°F, the bimetal strip inside the switch completes the circuit. This allows the ECU to determine if conditions are suitable for A/C operation. When the coolant temperature exceeds 235°F, the bimetal strip inside the switch opens circuit. This prevents the signal from being sent to the ECU.