Control Module HVAC: Description and Operation

The air conditioning amplifier controls the operations of the vacuum switching valve and the compressor clutch in response to signals received from the dual pressure switch, the coolant temperature switch, the thermistor and the engine control module (ECM). With the air conditioning system in operation, the air conditioning amplifier performs the following functions:

^ Energizes the compressor clutch in response to air conditioning system request and upon determination of favorable system conditions for air conditioning operation.
^ Control of engine idle speed during compressor operation.
^ De-energizes the compressor clutch in response to a high refrigerant pressure signal (from the dual pressure switch), a low refrigerant pressure signal (from the dual pressure switch), a high engine coolant temperature signal (from the coolant temperature switch), a low evaporator temperature signal (from the thermistor), or a high engine demand signal (from the ECM).