Air Distribution System

Air distribution system




The air distribution system distributes air to the passenger compartment. This is used jointly by the climate system's heating system and cooling system. The blower fan draws air into the system.
Fresh air is taken from the opening between the bonnet and the windscreen.
The air passes through the filter and the evaporator, past the temperature throttle valve and through the heat exchanger if necessary before it is released into the passenger compartment through the outlet.
After circulation the air leaves the passenger compartment via the pump-out valves in the cargo compartment.
The air distribution system consist of:
- distribution housing:
- blower fan
- throttle valve
- filter
- recirculation throttle valve
- air ducts
- outlets.
Three throttle valves control the outgoing air to:
- the defroster
- the ventilation outlets
- the floor outlets.

Blower fan




The blower fan provides the air flow through the vehicle. The blower fan must be running in order to switch on the air conditioning.
The fan motor is of a permanent magnet type. The impeller is of a radial type with a guide collar on the outer edge of the impeller. The impeller is balanced using steel clips. The blower fan features variable electronic control. The power unit is located separately below the fan motor.
The fan motor, on right-hand drive vehicles, is reversed compared to the fan motor on left-hand drive vehicles. The fan is accessed from the glove compartment. Special tools are required.

Throttle valve









Air is led from the fan through the different air ducts out to the passenger compartment by changing the direction of the throttle valve in the distribution housing.
The temperature is controlled by mixing hot and cold air.
ETC has a temperature damper that is regulated by a damper motor.
ECC has a split temperature damper. The two parts are each controlled by a damper motor. This makes it possible to have different temperatures on the driver's side and the passenger side. The dampers are regulated proportionally to ensure that the passenger compartment achieves the selected temperature.
The throttle valve is controlled by several Damper motor modules (DMM). For more information see Design and Function, Climate control module (CCM).

Recirculation throttle valve
The recirculation throttle valve controls the amount of incoming fresh air. The recirculation function makes it possible to prevent outdoor air from entering the passenger compartment, for example when the surrounding outer air is contaminated with exhaust fumes, smoke, etc. This function can also be used to quickly heat or cool the passenger compartment.
If the recirculation function is used for a long period of time the humidity in the passenger compartment increases. This is on account of the passengers' moist exhalation air. This can result in mist on the windows.
Automatic distribution and how much air is taken from the passenger compartment and how much air is taken from outdoors occurs in the control position max cooling. Distribution depends on the outdoor climate's temperature and humidity. This gives faster cooling of the passenger compartment air.
In vehicles with an air quality system (AQS), transfer to recirculation takes place automatically if the contamination content in the outdoor air increases.
There are two ways for the ventilation system to take in air:
- through fresh air from outside via the opening between the bonnet and the windscreen
- recirculated air from the passenger compartment.
Accordingly, the air distribution system has two air inlets. These are closed alternately by a flap (recirculation throttle valve).
The recirculation throttle valve is speed controlled, which means the throttle valve reduces the hole to the air inlet the greater the speed. This is done to maintain a constant air flow irrespective of the speed of the vehicle.

Filter




There are two types of filter:
- particle filter
- multi-filter.
The particle filter removes particles from the air, including dust and pollen, which otherwise would pass through the air inlet into the passenger compartment. The particle filter is standard.
The multi-filter is only available for vehicles with electronic climate control (ECC) and then in combination with the air quality sensor (AQS).
The multi-filter is a gas filter. It has the same function as the particle filter, but also neutralizes unpleasant odors and keeps the air as free as possible from gases. In vehicles with the multi-filter, so-called air quality system (AQS), there is also an outdoor sensor which ensures recirculation is closed should the outdoor air's gas content increase. This increases the service life of the multi-filter.
The filter is accessible from the right-hand side of the distribution housing.

Ventilation outlets




There are four ventilation outlets located on the dashboard. Two are placed in the middle and one on each side.
The B-pillars are also equipped with ventilation outlets.
The outlets are adjustable so that air can be restricted, blocked or guided in the appropriate direction.
If the side outlets are directed toward the side windows, this helps to keep the windows free from mist.

Defroster outlets
Mist is easily formed on the windows in cold air and damp weather. The defroster outlets release air toward the windscreen. The air flow removes any mist that forms. As the air is dry, the air flow also prevents moist air from the passenger compartment reaching the glass and with that counteracts mist formation. Air conditioning contributes greatly to these functions by dehumidifying the air at temperatures above 0 °C.
There on four defroster outlets, two for the windscreen and two for the front, side windows. The two for the windscreen are designed so the greatest part of the air goes up against the window. The remainder of the air seeps along the lower edge of the windscreen to help keep the windscreen wipers free from ice.
The air ducts to the side window defroster are a continuation of the windscreen's ducts.

Floor outlets
The four floor outlets release heated or chilled air by the driver's and passengers' feet.
Two of the floor outlets are placed in the centre under the sound wall, under the steering on the driver's side and in the centre under the glove compartment on the passenger's side. The other two are positioned under each seat and directed backward.

Pump-out valves
The pump-out valves are used to balance the pressure in the passenger compartment.
The pump-out valves are equipped with rubber flaps. The flaps open when the air pressure is slightly higher in the passenger compartment than outside. When the air pressure is as high on the inside is outside the flaps are closed. This prevents water from entering.
On 4-door vehicles the air outlets are located in the edge between the rear shelf and the rear window. The air goes from here through the cargo compartment and out through the pump-out valves behind the rear bumper.
In 5-door vehicles, the air passes directly out through the air vents in the cargo compartment.