XC90 AWD V8-4.4L VIN 85 B8444S (2005)
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 also:
The relay (2/22) closes the circuit between the integrated relay/fusebox in the engine compartment and the clutch for the air conditioning (A/C)
compressor (8/3). The air conditioning (A/C) compressor which has a variable cylinder displacement is always running during normal driving.
Displacement in the compressor is regulated by a solenoid which is controlled by the engine control module (ECM).
The engine control module (ECM) regulates the solenoid (displacement) in relation to the driver's and vehicles' different driving styles. Starting the
engine, moving off and acceleration means more regulated displacement so that the A/C compressor has less possible effect on engine torque. The
climate control module (CCM) controls all functions in the climate control module which are related to the vehicle interface with the driver and
passenger. I.E. the climate control buttons on the dashboard environment panel. Also see Design and Function, Climate control module (CCM).
The climate control module (CCM) transmits information to the engine control module (ECM), which determines what must be prioritized. For example,
the air conditioning (A/C) compressor in certain extreme cases is switched off completely, regardless of the climate control module (CCM) request. This
is to prevent negative engine performance and to protect the air conditioning (A/C) system. As well as the information from the climate control module
(CCM), the engine control module (ECM) controls the air conditioning (A/C) compressor based on the information from:
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Air conditioning (A/C) pressure sensor (high pressure side) (7/8)
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the throttle position (TP) sensor (6/120)
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the engine coolant temperature (ECT) sensor (7/16).
