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

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Description - Automatic Climate Control (ACC)

Heating Ventilation and Air Conditioning (HVAC) in a W220 S-Class is achieved by means of an electronically controlled Automatic Climate Control (ACC) system. The standard arrangement is a dual zone ACC with dual automatic or manual controls for temperature and air distribution. An optional four zone ACC is available.

Function - Automatic Climate Control (ACC)

The main functions of the ACC are:

Ventilation (Blower/s)

The low draft 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 by fully opening the front and rear foot well flaps 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.


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


  • The ACC compressor pumps refrigerant through the A/C gas circuit where most compression heat is removed in the condenser 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.

Special Features

  • Electrostatic dust and pollen air filters.
  • Activated Charcoal Filter with smog sensing automatic re-circulation of filtered cabin air.
  • Tunnel mode closes all windows, the sun-roof and incoming air vents via the re-circulation button or ACF button.
  • Humidity/dew-point sensor helps reduce window fogging during humid weather and helps prevent over drying of cooled air.
  • Four way sun sensor helps compensate for the effects of directional sun light on the occupants.
  • Seat belt usage sensors allows the ACC to focus first on occupied seating positions.
  • Automatic mode for center dash vents.

Main In Cabin Components - Automatic Climate Control (ACC)

Pushbutton Control Module (N22)

W220 2003 Pushbutton Control Module (N22) Celsius.JPG
W220 2003 Pushbutton Control Module (N22) Fahrenheit.JPG

Centre Vent Control Module (N18/4)

W220 2003 Centre Vent Control Module (N18 4) Front Compartment.JPG

Overhead Control Panel (OCP) (N70)

W220 2003 Overhead Control Panel (OCP) (N70).JPG

“B” Pillar Vents

W220 2003 Left “B” Pillar Vent Rear Compartment.JPG

Right Side Outlet and Fixed Window and Door Vents

W220 2003 Right Side Outlet and Fixed Window and Door Vents Front Compartment.JPG

Left and Right Defroster Vents

W220 2003 Left and Right Defroster Vents Front Compartment.JPG

Centre Vents with Optional A/C Control Module (N22/4) Rear Compartment

W220 2003 Centre Vents and Optional ACC Control Module (N22 4) Rear Compartment.JPG

Blower Motor (A32m1)

Reference STAR Finder document GF83.10-P-2102-02I Blower, function.

GF83.10-P-2102-02I W220 Blower Function.jpg

Blower Motor Regulator (A32n1)

Reference STAR Finder document GF83.10-P-2103-01I Blower regulator, function.

GF83.10-P-2103-011 W220 Blower Regulator Function.jpg

Thanks to BenzWorld Member cmitch, here is a photo of the Blower Regulator A32n1.

W220 Blower Regulator A32n1.JPG

Location - Blower Motor and Regulator

Reference STAR Finder document GF83.10-P-2103-01I Blower motor and regulator, location.

GF83.10-P-2103-02I W220 Blower Regulator Location.jpg

Circuit Diagram - Blower Motor and Regulator

Relevant part only shown.

W220 Blower Motor and Regulator Circuit Diagram.jpg

Main Engine Compartment Components - Automatic Climate Control (ACC)

Air Conditioning Compressor

Blower Fuse Connector X64/1

Located in Engine Compartment Right.

W220 X64 1 Blower Fuse Connector Location.jpg

Blower Fuse f33

Located in Engine Compartment Right Front Fuse and Relay Module (K40/7).

W220 K40 7 f33 Fuse Location.jpg

DIY Procedures - Automatic Climate Control (ACC)

Automatic Climate Control (ACC) Service Menus

Activated Charcoal Filter (ACF) or Aktivkohle Filter (AKF)


Cabin Ventilation Dust Filter

Coolant Circulation Pump

Duo Valve

Four Quadrant Sun Sensor (B32/2)

Pushbutton Control Module (N22)

In Cabin Air Temperature Sensor (N22/b1) and Aspirator in Pushbutton Control Module (N22)

Overhead Control Panel (OCP) (N70)

In Cabin Air Temperature Sensor (N70/b1) and Aspirator in Overhead Control Panel (OCP) (N70)

Multi-function Sensor (B31/1)

Outside Temperature Sensor (B14)

R134A Refrigerant Temperature Sensor (B12/1)

Repair Air Conditioning System

Under Hood ACC Drain Access and Cleaning

Evaporator Temperature Sensor (B10/6)

Evaporator temperature sensor A2208300772 (~EUR 15) is plugged in the left side of evaporator.

Error Code Generated By Description
B1256 AAC - Automatic air conditioning B10/6 (Evaporator temperature sensor), Evaporator Front
Temperature sensor unclipped.
Temperature sensor removed.

Entertainment - Automatic Climate Control (ACC)

How to replace W220 Evaporator Fantastic Video (Warning! Turn your sound down.)

Warning! Turn your sound down.