Ventilation system, function

S83.40-4569-05

Front ventilation function with CODE HH4 (THERMOTRONIC automatic climate control) or with CODE HH9 (Semi-automatically controlled air conditioning, TEMPMATIC)

The front ventilation ensures aeration of the front vehicle interior (air circulation) and also ensures the following conditions:

 the windshield and windows are kept defogged

 there is a good oxygen supply to occupants

 Constant and pleasant temperatures are quickly achieved in the front vehicle interior

Aeration can occur using one of the following two modes:

 Fresh air mode

 Recirculated air mode

Fresh air mode or air recirculation mode can be selected using the air recirculation mode button (S98/1s9). With the blower setting button (S98/1s3) and the air distribution button (S98/1s2) that is also integrated in the FRONT heater/air conditioning operating unit switch (S98/1), the air flow and the distribution of fresh and recirculated air is controlled.

To control the rate of circulation, the blower setting button is used to increase or reduce the output of the blower motor (M2) via the blower regulator, as required, in 7 stages. The output of the blower motor can also be increased or reduced automatically via the blower regulator by using the "AUTO" (S98/1s4) button.

 The air flow and the distribution can also be called up by using the A/C status line in radio (Audio/COMAND) (N87/6) in that the special functions, e.g. air distribution and ventilation modes fresh air/recirculated air, can also be selected, depending on the request.

 The air conditioning can be switched off via blower setting 0 in the respective menu in radio (Audio/COMAND).

The drawn in fresh or recirculated air in the front vehicle interior is then distributed, depending upon the request for air distribution, via the following air outlets:

 Left and right side window defroster vent

 Swiveling left and right side air vents

 Right and left footwell air outlets

 Windshield defroster vents

Fresh air mode

Fresh air mode is activated if the LED in the air recirculation mode button does not light up. The fresh air/recirculated air flap actuator motor (M2/5) puts the fresh air/recirculated air flap into "Fresh air open" position. In this position, the blower motor draws ambient air into the air conditioner housing via the right engine compartment air inlet grille, the interior air filter and the fresh air/recirculated air flap.

Recirculated air mode

The air recirculation mode is switched on when the LED in the air recirculation mode button lights up. The fresh air/recirculated air flap actuator motor puts the fresh air/recirculated air flap into "Recirculated air closed" position. In this position, the blower motor draws the recirculated air from the front vehicle interior into the air conditioner housing. Depending on the setting of the blower setting button and the setting of the left temperature selection button (S98/1s1), the right temperature selection button (S98/1s11) and the air distribution button, the recirculated air returns to the front vehicle interior through the air ducts and the air outlets.

If the outside temperature exceeds 20 °C, the automatic air conditioning (AAC [KLA]) control unit (N154) automatically switches to fresh air mode after approximately 30 minutes. If the outside temperature is below 20 °C, the system also switches automatically to fresh air mode after approximately 10 minutes.

Rear ventilation function with CODE HZ7 (Semi-automatically controlled air conditioning, TEMPMATIC in rear)

Additionally, temperature and air flow can be set individually for the rear area via the REAR heater/air conditioning operating unit switch (S98/2). The REAR heater/air conditioning operating unit switch is located in the center area of the headliner at the level of the B-pillar.

To control the rate of circulation, the rear blower button (S98/2s2) in the rear heater/air conditioning operating unit switch is used to increase or reduce the output of the rear blower motor (A32/4m1) via the rear blower regulator, as required, in 7 stages. The output of the rear blower motor can also be increased or reduced automatically via the rear blower regulator using the "AUTO" button in the FRONT heater/air conditioning operating unit switch.

 Air distribution is performed automatically, depending on the setting of the front unit and the operating mode. In automatic mode, the rear unit is set synchronously with the front unit to make sure the ideal thermal comfort is reached in the overall vehicle.

 The rear automatic air conditioning can also be controlled conveniently by the driver via radio (Audio/COMAND).

The distribution of the drawn in fresh or recirculated air is carried out via the following air outlets:

 Rear footwell vent at left rear

 Headliner, 2 vents at left

 Headliner, 2 vents at right

Function sequence for actuation of the air ducting flaps

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

The following air duct flaps are operated:

 Climate control with 1-zone temperature control with CODE HH9 (Semi-automatically controlled air conditioning, TEMPMATIC):

 Defroster/footwell/center air vent/side air vent flap via air distribution actuator motor (M2/15) (ventilation control)

 Blend air flap via blend air flap actuator motor (M2/14) (temperature control)

 Fresh air/recirculated air flap via the fresh air/recirculated air flap actuator motor (fresh air/recirculated air control)

 Climate control with 2-zone temperature control with CODE HH4 (THERMOTRONIC automatic climate control):

 Defroster/footwell/center air vent/side air vent flap via air distribution actuator motor (ventilation control)

 Left and right blend air flap via blend air flap actuator motors (temperature control)

 Fresh air/recirculated air flap via the fresh air/recirculated air flap actuator motor (fresh air/recirculated air control)

 Climate control with 2-zone temperature control with CODE HH9 (Semi-automatically controlled air conditioning, TEMPMATIC) and with CODE HZ7 (Semi-automatically controlled air conditioning, TEMPMATIC in rear)

 Defroster/footwell/center air vent/side air vent flap via air distribution actuator motor (ventilation control)

 Blend air flap over the blend air flap actuator motor (temperature control)

 Fresh air/recirculated air flap via the fresh air/recirculated air flap actuator motor (fresh air/recirculated air control)

 Footwell/roof vent flap via rear air distribution actuator motor (A32/4m2)

 Climate control with 3-zone temperature control with CODE HH4 (THERMOTRONIC automatic climate control):

 Defroster/footwell/center air vent/side air vent flap via air distribution actuator motor (ventilation control)

 Left and right blend air flap via blend air flap actuator motors (temperature control)

 Fresh air/recirculated air flap via the fresh air/recirculated air flap actuator motor (fresh air/recirculated air control)

 Rear fresh air/recirculated air flap via rear blend air flap actuator motor (A32/4m3) (fresh air/recirculated air control)

 Rear blend air flap via rear blend air flap actuator motor (temperature control)

 Footwell/roof vent flap via rear air distribution actuator motor

The automatic air conditioning (AAC [KLA]) control unit sends an "actuator motors" request via the climate control LIN 1 to the rear heater/air conditioning air recirculation unit (A32/4), which then directly actuates the actuator motors.

 The fresh air/recirculated air flap is closed after an accident (crash signal sent).

 The defroster/footwell/center air vent/side air vent flaps are operated via a linkage from the air distribution actuator motor.