An air conditioning system controls your car's temperature and works in a similar way to a kitchen refrigerator. When the refrigerant in these units changes from a liquid state to a gas, it cools down. Outside air is blown past the coils in which the gas flows, and is therefore also cooled before it is blown into the car’s cabin. The air con gas then returns to liquid form in the system's compressor, heating it up and directing the warm air outside the car.