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

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.

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 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)

Centre Vent Control Module (N18/4)

Overhead Control Panel (OCP) (N70)

“B” Pillar Vents

Right Side Outlet and Fixed Window and Door Vents

Left and Right Defroster Vents

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

Blower Motor (A32m1)

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

Blower Motor Regulator (A32n1)

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

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

Location - Blower Motor and Regulator

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

Circuit Diagram - Blower Motor and Regulator

Relevant part only shown.

Main Engine Compartment Components - Automatic Climate Control (ACC)

Blower Fuse Connector X64/1

Located in Engine Compartment Right.

Blower Fuse f33

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

DIY Procedures - Automatic Climate Control (ACC)

Multi-function Sensor (B31/1)

Location and Access - Multi-function Sensor (B31/1)

Remove two screws and gently withdraw the Multi-function Sensor (B31/1) located at right rear corner of engine compartment

RH Drive W220) adjacent to the fresh air intake.

Access and Testing - Multi-function Sensor (B31/1)

CO Carbon Monoxide Access and Testing (B31/1)

Multi-function Sensor (B31/1) CO Carbon Monoxide Access and Testing

Monitor Diagnostic Parameter NR.16: and breathe heavily on both sensors.
Start value: 683 which reduced to 681. 
Conclusion: Result is inconclusive.

Dew Point Temperature Access and Testing (B31/1)

Multi-function Sensor (B31/1) Dew Point Temperature Access and Testing

Monitor Diagnostic Parameter NR.18: and breathe heavily on both sensors.
Start value: 15.5 ºC which increased to 20.5 ºC.
Conclusion: Sensitivity of sensor seems OK.

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.

Replace Evaporator Temperature Sensor

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss Evap Temp Sensor Replacement Video (By Masood)

If your A/C suddenly starts to blow warm air, your Evap Temp Sensor may need to be replaced. If your S class A/C works for 10 minutes and then dies, and if this behavior continues every time you reset the A/C faults (video shows how to reset errors), you most certainly need to replace your Evap Temp Sensor.

You should also replace it as a very cheap maintenance item if your mileage is above 100,000 miles.

Part number is 220-830-07-72-M6 - you can purchase the Behr model from Pelican Parts at $16 as of 8/24/2019.

Entertainment - Automatic Climate Control (ACC)

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

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Warning! Turn your sound down.

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

Test the function of the In Car Temperature Sensor Control Module (N22)

Monitor Diagnostic Parameter NR.00: and place a pre-warmed hair drier over the slotted vent in the Pushbutton Control Module (N22).

Test Results
Start temperature: 26.3ºC which increased to 29.3ºC very quickly and then returned to 25.6ºC very quickly after the heat was removed.

Conclusion
Sensitivity of sensor seems OK.

Test the function of the Aspirator Motor for the In Car Temperature Sensor (N22/b1) in the Pushbutton Control Module (N22)

With the fan speed on manual Max 7 Bars, hold a narrow piece of tissue paper near the vented slots in the Pushbutton Control 
Module (N22) and note any tendency for the paper to be drawn onto the vent.

Test Results

The paper should adhere to the vent.