The function of an air conditioner is to help remove the heat and humidity from inside the passenger compartment of the vehicle. Powered by a belt, the air conditioning compressor compresses the refrigerant to pressurize it and pump it through the system. The refrigerant is pushed through a valve where pressure and temperature are reduced. The now-cool refrigerant travels through the evaporator in the passenger compartment. As a result, cooled air is blown into your vehicle. This refrigerant returns to the compressor, where the cycle begins once again.