Ventilation system, function

P83.10-2517-76

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

Function requirements, general

 Circuit 15 ON

 Status of circuit 15 is provided by EZS control unit (N73) via interior CAN (CAN B).

Ventilation, general

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.

When the fresh air/air recirculation flap is adjusted correspondingly, fresh air is supplied to the air conditioner housing via the air inlet. Depending on the current settings at the upper control panel control unit (N72/1), at the front central operating unit (A40/9) or at the rear air conditioning control unit (N22/4) (model 221 with code (582) Rear air conditioning), the air is routed through air ducts and air outlets into the vehicle interior.

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 With circuit 15 OFF, fresh air/recirculated flap is moved to
40 % for t = 2 min by fresh air/recirculated air flaps actuator motor (M2/5) when a door is opened. This achieves a significant reduction in the door closing forces.

 Fogging of the windows is prevented by closing the defroster vent flaps as well as the fresh air/recirculated air flap and by opening the footwell flaps t = 2 min after switching off circuit 15. After starting the engine, the defroster vent flaps and the footwell flaps remain in this fixed position for t = 30 s. The fresh air/air recirculation flap can be adjusted immediately. After that, all adjustments are possible again.

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The ventilation function consists of the following subfunctions:

 Function sequence for AC component actuation

 Fresh air mode function sequence

 Air recirculation mode function sequence

Function sequence for AC component actuation

The AC component actuation function sequence comprises the following subfunctions:

 Function sequence, actuation of the blower motor (A32m1) and the rear blower motor (M2/1) (on model 221 with code (582) Rear air conditioning)

 Function sequence for actuation of the air ducting flaps

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Function sequence for actuation of the blower motor and the rear blower motor (in model 221 with code (582) Rear air conditioning)

In accordance with the position of the fresh air/air recirculation flap, the interior air is circulated or fresh air is supplied by actuating the blower motor and the rear blower motor.

The blower motor is actuated by means of the blower regulator (A32n1), the rear blower motor is actuated by means of the rear air conditioning electronic blower regulator (N29/2) (model 221 with code (582) Rear air conditioning), in each case with the output regulated within a range of P = 0 to 100%.

The blower regulator is actuated via the climate control LIN (LIN B8) and the rear air conditioning electronic blower regulator (model 221 with code (582) Rear air conditioning) directly by the AAC [KLA] control unit (N22/1). Depending on the control voltage, the blower regulators control the operating voltage for the blower motor from U = 0 to 12.5 V and for the rear blower motor from U = 0 to 12 V, and thus the rpm of each blower motor from 0 to 100 %.

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 With voice control system active, the blower output is limited. For this, the COMAND controller unit (A40/3) sends the status of the voice control system via central CAN (CAN F) to the central gateway control unit (N93) and from here via interior CAN to the AAC [KLA] control unit. This then limits the blower output.

 On vehicles with code (B03) ECO start/stop function, the blower output is limited when the engine stops.

For this, the CDI control unit (N3/9) (with model 221 with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) sends the status "circuit 61 OFF" via chassis CAN (CAN E) to the EZS control unit and from there via interior CAN to the AAC [KLA] control unit. This then limits the blower output.

Air ducting flaps actuation function sequence

The air distribution in the vehicle interior is controlled by adjusting the air ducting flaps in the air conditioner housing.

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The following components are actuated by the AAC [KLA] control unit via climate control LIN:

- for fresh air/recirculated air control:

- Fresh air/air recirculation flaps actuator motor

- for temperature control:

- 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)

- for ventilation control:

- Left defroster flap actuator motor (M2/8)

- Right defroster 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 air vent flap actuator motor (M2/17)

- Right side air vent flap actuator motor (M2/18)

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- Left rear center air vent actuator motor (M16/19)
(model 221 with code (582) Rear air conditioning)

Right rear center air vent actuator motor (M16/20)
(model 221 with code (582) Rear air conditioning)

The left B-pillar air distribution actuator motor (M16/33) (model 221) and the right B-pillar air distribution actuator motor (M16/34) (model 221) are actuated via A/C bus (KB).

Fresh air mode function sequence

In fresh air mode, the fresh air/air recirculation flap is open and fresh air is delivered into the vehicle interior through the air conditioning housing.

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Air recirculation mode function sequence

The air recirculation mode function sequence comprises the following subfunctions:

 Function sequence, air recirculation mode via air recirculation button (N72/1s37)

 Pollutant-controlled air recirculation mode function sequence
(with code (581) Comfort automatic air conditioning)

Function sequence, air recirculation mode via the air recirculation button

Pressing the air recirculation button on the upper control panel control unit for t < 1.5 s closes the fresh air/air recirculation flap and thus prevents the supply of outside air. The air only circulates in the vehicle interior and unpleasant odors and harmful gases are kept out. The LED in the air recirculation button comes on.

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Pressing the air recirculation button for t > 1.5 s activates comfort recirculation closing. As a result, the windows and the tilting/sliding roof (SHD) (model 216 or model 221 with code (414) Power glass tilting/sliding roof) or the panoramic sliding sunroof (model 221.1 with code (413) Panoramic glass sunroof with top sliding sunroof) are closed.

When the air recirculation button is pressed again for t > 1.5 s, the windows and the tilting/sliding roof or the panoramic sliding sunroof return to the previous positions.

 On vehicles with code (460) Canada version and code (494) USA version, comfort recirculation closing is not possible.

 The detailed procedure of the comfort recirculation closing function is described in the comfort feature function (KFB).

Additional function requirements for pollutant-controlled air recirculation mode (with code (581) Comfort automatic air conditioning)

 Refrigerant compressor (A9) switched on

 Defrost mode not active

 Outside temperature T > 5 °C

Function sequence for pollutant-controlled air recirculation mode
(with code (581) Comfort automatic air conditioning)

The pollutant concentration in the outside air is measured by the AAC [KLA] multifunction sensor (B31/1). The data of the AAC [KLA] multifunction sensor are read in by the AAC [KLA] control unit via the A/C bus.

Starting from a certain increase in pollutant concentration, the fresh air/recirculated air flap is automatically set to the air recirculation position by the AAC [KLA] control unit. Outside air supply is prevented and only the inside air is recirculated.