How Your Car's Air Conditioner Works

Once an expensive luxury for the well-heeled, air conditioning is now a commonplace comfort in nearly all types of vehicles. A car's A/C unit cools and dehumidifies air which enters the cabin. The first systems were relatively simple and easy to repair, but the introduction of computerized temperature control and other assembly modifications has changed that. Today's do-it-yourself auto enthusiasts are rarely able to repair the units.

Below, we'll take a brief tour through your vehicle's A/C unit. We'll explore the components that work together as well as the refrigerant which cools the air. The information I'll provide is merely a glimpse. While you won't be able to repair your vehicle's A/C, you will at least be informed when you visit your mechanic.

How The A/C's Components Work Together

The heart of your car's A/C system is the compressor, a belt-driven pump that compresses and moves the refrigerant. A refrigerant is a chemical compound that is used to transfer heat, during which it undergoes a phase change from gas to liquid and vice versa.

Along with the compressor, the condenser is necessary for heat dissipation. As the refrigerant leaves the compressor, the heat absorbed from the cabin causes it to expand into a gas. Traveling along the condenser coils, the fluid proceeds to change back into a liquid. Because a condenser requires maximum air flow to enable heat dissipation, the part is often mounted in front of the radiator (though its position can vary). In addition to the mounting point, some vehicles have incorporated a cooling fan as well.

The evaporator also plays an important role in your vehicle's air conditioner. This device removes heat from the inside of your car and provides a small degree of dehumidification. The evaporator assembly has an array of aluminum fins that allow water contained within the air to condense. When the water condenses, pollen, dust, and other particulates are trapped by the droplets which are then drained off and released under the car.

Refrigerant Maintenance

When the first air conditioning units were introduced, the refrigerant R-12 was used. Otherwise known as Freon, this odorless, colorless chlorofluorocarbon was discovered to damage the ozone layer. Since the 1990s, most Freon applications have been phased out due to government regulation.

In the event of an air conditioner malfunction on an older car, the fluid may have to be replaced with an environmentally-friendly alternative. Currently, this means retrofitting the old system for R-134a, a refrigerant that won't harm the ozone layer. However, this new fluid will have a higher operating pressure and will therefore require new, stronger parts. In some cases, parts may not necessarily have to be replaced depending on the fluid change.

If you notice that your car's A/C system isn't cooling the cabin as quickly or effectively as it used to, ask your mechanic to run a test. It's likely that the refrigerant needs to be replenished. That said, if your A/C is failing, plan to spend at least $200.

Tags:Cars, Autos. Vehicles, Car Air Conditioner, Car Maintenance, Car Repair