Ventilation system, function - GF83.10-P-2000SX

MODEL 216.3, 221.0 /1 up to Model Year 8 

Shown on model 221.0 with code (582) Rear air conditioner 

Fig 1: Identifying Ventilation System Function Diagram

Courtesy of MERCEDES-BENZ USA

Function 

The ventilation system prevents windows from misting up, supplies air to the vehicle occupants, and ensures that uniform and pleasant temperatures in the vehicle interior are reached quickly.

Ventilation is achieved with the support of the blower motor (A32m1) during normal operation, when vehicle is stationary or to increase the air flow. When the fresh air/air recirculation flap is adjusted correspondingly, fresh air is supplied to the air conditioner housing via the air inlet in the engine hood.

The output of the blower motor is controlled by the blower regulator (A32n1). Depending on the preselection on the upper control panel control unit (N72/1), on the front central operating unit (A40/9) or on the rear air conditioning control unit (N22/4) (with code (582) Rear air conditioner), the air is routed through air ducts and air outlets into the vehicle interior.

The air distribution in the vehicle interior is controlled by corresponding adjustment of the air duct flaps in the air conditioner housing.

With code (582) Rear air conditioner, ventilation of the rear compartment is achieved with the rear blower motor (M2/1).

Depending on the request, the following components are actuated by the AAC [KLA] control unit (N22/1) via the AC LIN:

• Fresh air flap/recirculated air flap actuator motor (M2/5)
• Left defroster vent flap actuator motor (M2/8)
• Right defroster vent flap actuator motor (M2/9)
• Left footwell flap actuator motor (M2/10)
• Right footwell flap actuator motor (M2/11)
• Left center air flap actuator motor (M2/12)
• Right center air flap actuator motor (M2/13)
• Left side outlet flap actuator motor (M2/17)
• Right side outlet flap actuator motor (M2/18)
• Upper left blend air flap actuator motor (M2/30)
• Lower left blend air flap actuator motor (M2/31)
• Upper right blend air flap actuator motor (M2/32)
• Lower right blend air flap actuator motor (M2/33)
• Left B-pillar air distribution actuator motor (M16/33) (model 221)
• Right B-pillar air distribution actuator motor (M16/34) (model 221)

The ventilation function allows the following operating modes: 

• Fresh air mode
• Air recirculation mode
• Pollutant-controlled air recirculation mode

Recirculation mode 

Briefly pressing the air recirculation button (N72/1s37) at the upper control panel control unit closes the fresh air/air recirculation flap and thus prevents outside air supply. The air only circulates in the vehicle interior and unpleasant odors and harmful gases are kept out. The "Air recirculation" LED comes on during operation.

Pollutant-controlled air recirculation mode 

The C-AAC [K-KLA] multifunction sensor (B31/1) sends the outside air pollutant values to the AAC [KLA] control unit.

The AAC [KLA] control unit decides, also taking the moisture and temperature values into consideration, on the position of the fresh air/air recirculation flap.

Starting from a certain pollutant concentration, the fresh air/air recirculation flap is automatically set to recirculated air.

The windows and the tilting/sliding roof (SHD) (model 221 with code (414) Power glass tilting/sliding roof or model 216) or the panoramic roof (model 221 with code (413) panoramic glass roof with top sliding roof) are automatically closed.

By pressing the air recirculation button or after a certain period of time has elapsed, the fresh air/air recirculation flap is set to fresh air. However, the windows and the tilting/sliding roof (SHD) or the panoramic roof remain closed. The "Air recirculation" LED goes out.

Recirculated air convenience feature 

After pressing the air recirculation button for more than 1.5 s, the windows and the SHD or the panoramic roof are automatically closed. When the air recirculation button is actuated again, the system moves the windows and the SHD back to their previous positions.

The convenience closing function is only available to a limited extent for vehicles with panoramic roof. For this purpose, the air recirculation button has to be pressed and held down as long as the convenience feature is actuated.

Defrosting (Defrost) 

The defrosting function serves for keeping the windows free of fog or quickly defogging windows by actuating the defroster outlet flap to the full open position and closing the footwell flaps. Additionally, the refrigerant compressor (A9) is engaged. The fresh air/air recirculation flap is set to fresh air, the air conditioner water valve (Y19/2) is opened, and the coolant circulation pump (M13) and if necessary the PTC heater booster (R22/3) (with diesel engine) are actuated.

If the "Defrost" function is active, the settings for temperature, air distribution, recirculated air and AC are locked. With code (582) Rear air conditioner, the symbols "OFF" and "Rear remote control" appear in the display of the rear air conditioning control unit. The rear air conditioner is switched off. The buttons of the rear air conditioning control unit are not locked.

Fresh air mode 

During fresh air mode, the fresh air/air recirculation flap is in the fresh air position.

The blower motor delivers outside air into the vehicle interior.