XC70 AWD L6-3.2L VIN 98 B6324S (2009)
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) controls the solenoid (displacement) from the driver's and vehicle's various driving characteristics. On Startup of the
engine, pulling off and at acceleration etc, displacement is controlled so that the A/C compressor has the least possible effect on the engine torque. The
climate control module (CCM) controls all functions in the climate control system that are related to the vehicle's interface for driver and passenger. I.E.
the climate control system buttons on the dashboard environment panel. Also see Design and Function, central electronic module (CEM).
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:
Air conditioning (A/C) pressure sensor (high pressure side) (7/8)
the throttle position (TP) sensor (6/120)
the engine coolant temperature (ECT) sensor (7/16).
To ensure that the correct throttle angle is reached, the engine control module (ECM) (4/46) controls the throttle shutter in the throttle unit (6/120),
mainly using the signal from:
accelerator pedal (AP) position sensor (7/51)
the throttle position (TP) sensor on the electronic throttle unit.
Additional signals and parameters are used to ensure optimum throttle control. By example by compensating for:
the load from the air conditioning (A/C) compressor
the load from the transmission depending on the selected gear mode
engine coolant temperature (ECT)
mass air flow through the intake manifold
manifold absolute pressure (MAP) in the intake manifold.
The position of the throttle is measured by two potentiometers, in the throttle position (TP) sensor, which are on the throttle unit. These are connected, so
that potentiometer 1 produces a higher voltage as the throttle angle increases, while potentiometer 2 does the opposite.
In a combustion engine, the difference between the minimum and maximum airflow is considerable. The smaller air flows need more thorough
regulation, so the potentiometer signal from potentiometer 1 is amplified approximately 4 times in the engine control module (ECM) before it reaches the
AC/DC converter in the engine control module (ECM). This means that there are three, two real and one fictitious, input signals available to the engine
control module (ECM). These signals are used to determine the position of the throttle and to deploy the damper motor to the correct position. In general
the amplified signal is primarily used for small throttle angles (small air flows), which are desirable when a high degree of accuracy is required, for idle
air trim for example.
Because the signal is amplified, it reaches its maximum value as early as approximately a quarter of maximum deployment.