Ventilation system, function

D83.10-1124-05

Shown with code (H13) Additional heat exchanger in load compartment

1 Defroster outlet for left side window

2 Adjustable left side air outlet

3 Adjustment wheel for left side air outlet

4 Adjustable left center nozzle

5 Adjustment wheel for left center nozzle

6 Air vent for left head area and rear passenger compartment

7 Adjustment wheel for air supply for air vents in left head area and rear passenger compartment

8 Air vent for right head area and rear passenger compartment

9 Adjustment wheel for air supply for air vents in right head area and rear passenger compartment

10 Adjustable right center nozzle

11 Adjustment wheel for right center nozzle

12 Adjustment wheel for right side air outlet

13 Adjustable right side air outlet

14 Defroster outlet for right side window

98/1 Front temperature selection switch

98/3 Air distribution switch

S98 AAC [KLA] control and operating unit

S98s1 Blower switch

S98s6 Air recirculation mode button

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

 the windshield and windows are kept defogged

 there is a good oxygen supply to occupants

 constant and pleasant temperatures are quickly achieved in the vehicle interior

Aeration can occur using one of the following two modes:

 Fresh air mode

 Air recirculation mode

Selection is made using the air recirculation mode button. The rate of circulation and distribution of the fresh air or recirculated air are regulated using the blower switch and the air distribution switch, which are integrated into the AAC [KLA] control and operating unit. The rate of circulation is regulated by the blower switch which regulates the output of the blower motor (M2).

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To regulate the rate of circulation, the blower switch can adjust the output of the blower motor in the following five stages via the blower motor series resistor group (R14):

 Stage 0

 Stage 1

 Stage 2

 Stage 3

 Stage 4

Distribution of the aspirated fresh air or the recirculated air can be regulated by the air distribution flaps via the air distribution switch. The distribution of the suctioned fresh or recirculated air is possible in the following positions:

 Defroster vents (12:00 o'clock position)

 Defroster vents and footwell vents (3 o'clock position)

 Footwell vents (6 o'clock position)

 Dash support vents (9 o'clock position)

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 Intermediate positions are also possible in addition to the listed ones, e.g., when the air distribution switch is in between the defroster vent (12 o'clock position) and the defroster vent and footwell vent position (3 o'clock position).

The aspirated fresh air or recirculated air in the vehicle interior is then distributed, depending on the position of the air distribution switch, via the following air outlets:

 Defroster outlet for left side window

 Adjustable left side air outlet

 Adjustable left center nozzle

 Air vents for left head area and rear compartment

 Air vents for right head area and rear compartment

 Adjustable right center nozzle

 Adjustable right side air outlet

 Defroster outlet for right side window

 Right and left footwell air outlets

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 Outlet of fresh or recirculated air is also dependent on the position of the following adjustment wheels:

 Adjustment wheel for left side air outlet

 Adjustment wheel for left center nozzle

 Adjustment wheel for air admixture air vent in left head area and rear passenger compartment

 Adjustment wheel for air admixture air vent in right head area and rear passenger compartment

 Adjustment wheel for right center nozzle

 Adjustment wheel for right side air outlet

Fresh air mode

The fresh air mode is selected, when the red light emitting diode (LED) in the air recirculation mode button is not on. In the fresh air mode, the fresh air/air recirculation flap actuator motor (M16/21) keeps the fresh air and air recirculation flap open in the fresh air position.

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In this position, ambient air is sucked into the front heater housing with the aid of the blower motor via the right air inlet in the engine hood, the particulate filter (for vehicles with code (H81) Ventilation system with filter) and via the fresh air and air recirculation flap.

Depending upon the position of the blower switch, the front temperature selector switch and the air distribution switch, fresh air reaches the vehicle interior through the air ducts and the air outlets. On model 906.6/7 the fresh air escapes from the vehicle through the two vent flaps integrated into the left rear D-pillar and in the right rear D-pillar. On model 906.1/2 the fresh air escapes through the two vent flaps attached to the cab rear wall.

Recirculation mode

The air recirculation mode is selected, when the red LED in the Air recirculation mode button lights up. In air recirculation mode the fresh air/air recirculation flap actuator motor keeps the fresh air and air recirculation flap in the recirculated air position. In this position, recirculated air is sucked out of the vehicle interior into the front heater housing with the aid of the blower motor.

Depending upon the position of the blower switch, the front temperature selector switch and the air distribution switch, recirculated air reaches the vehicle interior through the air ducts and air outlets.