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A car's air conditioning system does not create cold air. Instead, it takes the heat out of air that is already in your car. Understanding how this works begins with understanding the various components of an automotive air conditioning system. The large central component is called a compressor. Coming out from the compressor are high-pressure and low-pressure hoses. These hoses run to the condenser, which looks like a small radiator toward the front of the engine, and an evaporator, which also looks like a small radiator. The system also has a dryer, which looks like a small canister. Finally, the system has a thermal expansion valve, which is responsible for controlling the flow of refrigerant through the system, thus regulating the temperature of the air. Coolant, which is a compressible gas, runs through this system.

The coolant, which is often Freon, begins in the compressor, where it is compressed into a high-pressure, high-temperature gas. It travels through the high-pressure lines to the condenser. The condenser puts the gas in contact with fresh air on the outside of the vehicle, which absorbs the heat from the gas. This causes the refrigerant to liquefy, but it is still at high pressure. It then flows into the dryer, where the liquid is separated from any other gases or impurities that have made their way into it during the process. The clean liquid then travels through the tubing into the evaporator, where it turns into vapor. Fans blow the air from the car's cabin over the evaporator, and the evaporating liquid sucks the heat out of the air to use as energy for the evaporation process. The cool, dry air is recirculated back into the cabin, while the refrigerant, now in low-pressure gas form, heads back to the compressor to get compressed into the high-pressure gas and begin the process again.

The Potential Dangers

Car air conditioners rely on compressible gases, such as Freon. The type of Freon that was commonly used in cars in the past, R-12, is harmful to the ozone layer. As such, it cannot be exposed to the air, which means servicing car air conditioners requires access to special machines that keep the Freon out of the atmosphere. Newer cars are being cooled with a new refrigerant, R-134a. This is not dangerous to the ozone layer, and thus can be serviced without special tools. Many cars can be converted to use the less dangerous refrigerant.

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