WIS 83.40 Automatic Climate Control (ACC) or Heating Ventilation and Air Conditioning (HVAC)

Description - Automatic Climate Control (ACC)

The Heating Ventilation and Air Conditioning (HVAC) in a W220 S-Class is achieved by means of an electronically controlled Automatic Climate Control (ACC) system.

Function - Automatic Climate Control (ACC)

The main functions of the ACC are:

Ventilation

The ventilation system:

Is achieved by the ACC blower or the rear A/C blower.
Looks after the air distribution in the vehicle interior.
Supplies fresh or recirculated filtered air to the vehicle interior.
Maintains a quick, quiet and comfortable vehicle interior.
Distributes air within the vehicle via air distribution flaps.
Prevents windows from fogging. The front foot well flaps and the rear foot well flaps are fully opened for 30s after the ignition is switched on.

Temperature Control

The desired temperature is maintained by heating the air by operating the duo valves.
The desired temperature is maintained by cooling the air by operating the refrigerant compressor.
The basic temperature setting is 22ºC
Accurate temperature control is achieved by monitoring the various temperature sensors such as:
- Left Heat Exchanger Temperature Sensor (B10/2)
- Right Heat Exchanger Temperature Sensor (B10/3)
- Evaporator Temperature Sensor (B10/6)
- Outside Temperature Sensor (B14)
- Sun Sensor (B32/2)
- Interior Temperature Sensor in ACC Pushbutton Control Module (N22) (N22/b1)
- Interior Temperature Sensor in Overhead Control Panel (OCP) (N70) (N70/b1)
- Temperature Sensor in Rear A/C Evaporator outlet for vehicles fitted with Code 582.

Electronic Control

The ACC is controlled electronically by several control modules which are connected to the Can B (Interior) Bus. Each control module receives and sends digital messages across the CAN Bus.

Operator Control

The ACC can be operated by pressing buttons on the ACC Pushbutton Control Module (N22) or on the Rear A/C in vehicles fitted with Code 582.
The push button control module reads input from the sensors and actuates ACC components.

Heating

Coolant which has been heated by the engine is pumped through the front and rear heat exchangers.

Cooling

The ACC compressor pumps refrigerant through the A/C gas circuit where most compression heat is removed in the condenser evaporator and then the refrigerant is expanded through a valve into the evaporator where it absorbs heat from the ACC air flow.

Residual Heating/Cooling

The REST button on the ACC Pushbutton Control Module (N22) allows limited heating and cooling of the vehicle interior even if the ignition is Off.
The ACC blower runs for about 30 minutes and distributes residual heat or cool into the passenger compartment.