The Purpose of the Saab AC system is to lower the air temperature within the cabin of the vehicle during high outside temperature conditions. The AC compressor actually decreases the humidity of the inside air during damp conditions which also aid in defrosting the interior windows. Most people think that the AC system produces cold air but in reality the AC system simply cools the air coming into the car instead. This effect is accomplished by running a cooling agent (such as freon R134 or R12) through a finned item (called an evaporator) and then blowing the air over those fins to cool the air off as it enters the car. The basics are: The AC compressor is turned on and driven by the belt, after the cabin fan motor is turned on the air is blown over cooled fins of the AC evaporator which in turn cools down the air that is entering the vehicle to cool down the interior cabin air.