Air Conditioning Compressor
Back to: WIS 83.40 Automatic Climate Control (ACC) or Heating Ventilation and Air Conditioning (HVAC)
Description - Air Conditioning Compressor
The W220 uses a Variable Displacement Compressor (A9) in which the volume is varied between 2% (minimum stroke value) and 100% (maximum stroke value) by the externally controlled A/C compressor valve.
The appropriate Pulse Width Modulated (PWM) signal is sent to the compressor control valve via the ACC push-button control module, depending on the refrigeration requirements.
The refrigeration requirement is determined primarily by the temperature settings for the vehicle's passenger compartment and the values measured by the in-car temperature sensors.
The following will affect the PWM signal sent to the compressor control valve.
- Selected temperatures on the ACC Pushbutton Control Module (N22),
- In-car temperature sensors,
- Humidity,
- Sun intensity,
- Outside temperature,
- Evaporator temperature, and the
- Engine coolant temperature.
Description - Air Conditioning Drive Pulley
The W220 Air Conditioning Drive Pulley which couples the compressor to the Serpentine Belt does not employ an electro-magnetic clutch. Instead the compressor rotates continuously at a speed similar to the engine RPM and the quantity of cooling achieved is determined by the setting of the variable displacement in the compressor.
In the event of a compressor failure which causes the compressor to seize, the Air Conditioning Drive Pulley is designed with a rubber coupling element between the drive pulley grooves and the compressor crankshaft which can distort or even fracture thus decoupling the compressor from the engine drive.