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.