Regulating The Air Conditioning (A/C) Compressor

Fig 1: Identifying Air Conditioning (A/C) Compressor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The air conditioning (A/C) compressor is controlled by the engine control module (ECM) (4/46) on request from the climate control module (CCM) (3/112) via the controller area network (CAN). When the engine control module (ECM) receives a signal from the climate control module (CCM) to activate the air conditioning (A/C) compressor, the engine control module (ECM) grounds the circuit for the relay coil for the A/C compressor. See: AIR CONDITIONING (A/C) RELAY 

The relay (2/22) closes the circuit between the integrated relay/fusebox in the engine compartment and the clutch for the A/C compressor (8/3).

In addition to the information from the climate control module (CCM), the engine control module (ECM) checks the engagement and disengagement of the A/C compressor based on:

• the signal from the air conditioning (A/C) pressure sensor (high pressure side) (7/8)
• the signal from the air conditioning (A/C) pressure sensor (low pressure side) (8/119)
• the throttle position (TP) sensor (6/120)
• the engine coolant temperature (ECT) sensor (7/16).