Ventilation system, function

The ventilation ensures aeration of the 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 vehicle interior

Aeration can occur using one of the following two modes:

 Fresh air mode

 Recirculated air mode

The fresh air/air recirculation mode selection is made using the air recirculation mode and air distribution rotary switch. The rate of circulation and the distribution of fresh/recirculated air are controlled with the blower knurled wheel switch (A81s2) and the air recirculation mode and air distribution rotary switch which are integrated in the climate control control and operating unit (A81).

To control of the rate of circulation, the output of the front blower motor (M4) is increased or decreased by the blower knurled wheel switch. To control of the rate of circulation, the blower knurled wheel switch can be used to set the output of the front blower motor using the blower settings 1-3 series resistor (R10) in the following 5 stages:

 Stage 0 (blower "OFF")

 Stage 1

 Stage 2

 Stage 3

 Stage 4 (max. blower output)

The distribution of the drawn in fresh or recirculated air is controlled with the recirculated air solenoid valve (Y95) via the air recirculation mode and air distribution rotary switch.

The distribution of the suctioned fresh or recirculated air is possible in the following positions:

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

 Footwell vents (6 o'clock position)

 All vents closed (9 o'clock position)

 Dash and defroster vents (12 o'clock position)

 Intermediate positions are also possible in addition to the listed ones. E.g. when the air recirculation mode and air distribution rotary switch is in between the dash and defroster vents (12 o'clock position) and the dash vents and footwell vents position (3 o'clock position).

The drawn in fresh or recirculated air in the vehicle interior is then distributed depending on the position of the air recirculation mode and air distribution rotary switch using the following air outlets:

 Left side window defroster vent

 Adjustable left side air outlet

 Air vent for left head area and rear passenger compartment

 Air vent for right head area and rear passenger compartment

 Adjustable right center nozzle

 Adjustable right side air outlet

 Right side window defroster vent

 Right and left footwell air outlets

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

 Left side vent control

 Left center vent control

 Control for air admixture air vent for left head area and rear passenger compartment

 Control for air admixture air vent for right head area and rear passenger compartment

 Right center vent control

 Right side vent control

Fresh air mode

Fresh air mode is activated if the LED in the air recirculation mode and air distribution rotary switch is not lit. The recirculated air solenoid valve sets the fresh air/recirculated air flap to the "Fresh air open" position. In this position, the front blower motor draws the ambient air into the air conditioner housing via the air inlet grille above the engine hood, the pollen filter and the fresh air/recirculated air flap.

Recirculated air mode

Air recirculation mode is switched on if the LED in the air recirculation mode and air distribution rotary switch is lit. The recirculated air solenoid valve sets the fresh air/recirculated air flap to the "Recirculated air closed" position. In this position, the front blower motor draws the recirculated air from the vehicle interior into the air conditioner housing. Depending on the setting of the blower knurled wheel switch as well as the position of the temperature control and the air recirculation mode and air distribution rotary switch, the recirculated air is then routed through the air ducts and the air outlets back into the vehicle interior.

The climate control control and operating unit reads in the outside temperature sensor (B37) via engine CAN (CAN C) from the instrument cluster (P15) and automatically switches to fresh air mode if the outside temperature is above 20 °C after approx. 30 min. If the outside temperature is below 20 °C, the system also switches automatically to fresh air mode after approx.10 min.