Ventilation system, function

P83.10-2654-05

Air outlets in passenger compartment

General function requirements

 Circuit 15 On

General ventilation system

The ventilation ensures fog-free windows, air supply to the vehicle occupants and that uniform and pleasant temperatures are reached quickly in the vehicle interior.

When the fresh air/air recirculation flap is adjusted correspondingly, fresh air is supplied to the heater or air conditioning box via the air inlet. Depending on the current settings at the automatic heater control and operating unit (N18) (without code (580) Automatic air conditioning and without code (581) Comfort automatic air conditioning), at the AAC [KLA] control and operating unit (N22) (with code (580) Automatic air conditioning) or at the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning), the air is routed through air ducts and air outlets into the vehicle interior.

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 In order to prevent fogging of windows, the defroster vent flaps and the fresh air/recirculation flap are closed and the footwell flaps fully opened 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. After that, all adjustments are possible again. The fresh air/air recirculation flap can be adjusted immediately.

The ventilation system comprises the following subfunctions:

 AC component actuation function sequence

 Fresh air mode function sequence

 Air recirculation mode function sequence

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AC component actuation function sequence

The AC component actuation function sequence comprises the following subfunctions:

 Function sequence for actuation of the blower motor (A32m1)

 Function sequence, actuation of the air ducting flaps

Function sequence for actuation of the blower motor

Ventilation is achieved with the aid of the blower motor. The control and operating unit transmits a signal from 0 to 100 % via the AC bus to the blower regulator (A32n1). Depending on the control voltage, the blower regulator regulates the operating voltage for the blower motor from U = 0 V up to U = 12 V and thus the rotational speed of the blower motor from 0 up to
100 %.

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Air ducting flaps actuation function sequence

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

The control and operating unit actuates the following components via the AC bus:

- for fresh air/air recirculation control:

- Fresh air/air recirculation flap actuator motor (M2/5)

- for ventilation control:

- Left and right footwell flaps actuator motor (M2/15)

- Left and right defroster flaps actuator motor (M2/16)

- Air flaps actuator motor (M2/21)
(with code (581) Comfort automatic air conditioning)

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Fresh air mode function sequence

The fresh air/air recirculation flap is open and fresh air is delivered into the vehicle interior through the heater or air conditioning box.

Additional function requirements for air recirculation mode

 Vario roof closed

 Side windows closed

Air recirculation mode function sequence

The air recirculation mode function sequence comprises the following subfunctions:

 Function sequence for air recirculation mode via the air recirculation switch (N18s2) (without code (580) Automatic air conditioning and without code (581) Comfort automatic air conditioning), the air recirculation switch (N22s2) (with code (580) Automatic air conditioning) or the air recirculation switch (N22/7s2) (with code (581) Comfort automatic air conditioning)

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

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Function sequence for air recirculation mode via air recirculation switch

When the air recirculation switch on the control and operating unit is pressed for t < 1.5 s, the fresh air/air recirculation flap is closed, and thus the supply of outside air is prevented. The air only circulates in the vehicle interior and unpleasant odors and harmful gases are kept out. The light-emitting diode in the air recirculation switch comes on.

Pressing the air recirculation switch for t > 1.5 s automatically closes the side windows (comfort recirculation closing). If the air recirculation switch is pressed again for t > 1.5 s, they return to the previous position.

 Windows that were manually opened during the air recirculation mode are not returned to the previous position after the air recirculation mode is ended.

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

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

Additional function requirements for pollutant-controlled air recirculation mode

 Refrigerant compressor (A9) switched on

 Defrost mode not active

Pollutant-controlled air recirculation mode function sequence

The comfort automatic air conditioning multifunction sensor (B31) transmits the outside air pollutant values via the AC bus to the control and operating unit. Starting from a certain pollutant concentration, the fresh air/air recirculation flap is automatically set to the recirculated air position. Outside air supply is prevented and only the inside air is recirculated.

If after starting the engine the condition for pollutant-controlled air recirculation mode is given, then fresh air is supplied for t =
30 s. Following this, operation continues with 80 % pollutant-controlled recirculated air and after another t = 10 s, as required, with 100 % pollutant-controlled recirculated air. The pollutant-controlled air recirculation mode is not displayed via the LED.