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Understanding How Your Cars A/C System Works



Without an A/C system in a car, there’s hardly any opportunity for a comfortable ride. Thanks to our ability to change our environment to better suit our whims, we can take a ride on a hot summer day with the A/C on full blast without a care in the world. But then, how does our car actually manage to create air currents far colder than the ambient temperature? Surely, it isn’t just a matter of a few high-powered fans underneath our hood doing all of the hard work, right?

As it turns out, the A/C system in a car is a relatively complex piece of equipment that uses a complex chemical reaction to cool air and deliver it to the car’s cabin to be enjoyed. The A/C system is an entirely self-contained series of components that don’t take up too much space in the vehicle overall. With just some refrigerant and a few key components, cool air can be delivered in a surprisingly short amount of time.

Let’s take a look at this entire process, as well as the steps involved:

Refrigerant is the key

The entire A/C system is filled with refrigerant gas. These days, it’s typically a gas known as R-134a or Freon, but in the past, other refrigerants were used until their ozone-depleting qualities were discovered. This refrigerant is either heated or cooled by abusing its chemical properties, and then, that heat/cold is used to change the temperature of air further down the line, which is then blown into the cabin.

It all starts at the compressor

The beginning of the process is at the compressor. The compressor works to compress the ambient refrigerant gas, which can then be sent to the condenser. When the gas is compressed, it becomes very hot, which is when the condenser comes into play.

Hot refrigerant is cooled by the condenser

After being compressed, the gas is sent through the condenser. A condenser is essentially a series of coils surrounded by outside air that works to remove the heat from the gas, so it begins to condense into a liquid. A condenser that’s parallel in its construction can’t be flushed and needs to be replaced in the event of failure. Serpentine condensers can be flushed, which means they need to be replaced less often than their parallel-style equivalents.

The receiver-drier and the AC inline filter

The receiver-drier is a small canister within your A/C system that contains desiccant meant to remove moisture from the air that flows through the system. This way, excess moisture is dealt with, and the humidity of the blown air will be managed as well. Another component known as the AC inline filter also picks up debris within the system itself. These two components are essential in maintaining the overall functioning of your system.

Liquid refrigerant is then turned into a mist

The liquid refrigerant now passes through the expansion valve, which changes it from a high-pressure liquid to a low-pressure liquid. So it may then pass through the evaporator. Some vehicles use an orifice tube instead of an expansion valve. But both of these pieces of equipment simply restrict the flow of the liquid in such a way that it’s converted from high-pressure liquid to low-pressure liquid.

Cabin is treated with the evaporator

This low-pressure mist is then blown through the evaporator which is a series of tubes that are cooled. Thanks to the movement of this low-pressure mist. Another blower is above the evaporator. Which blows cold air from above the tubes into the passenger cabin of the automobile.

It ends at the accumulator

The accumulator works as a place for the refrigerant exiting the evaporator before it’s reused in the system. Within the accumulator is a desiccant bag meant to remove any moisture that may be present after going through the evaporator.

That’s how the actual system works from end to end. Pretty interesting. It’s essentially just abusing how refrigerant can be rapidly made hot or cold. Then blowing air exposed to those temperatures into the passenger cabin. After the refrigerant goes through the accumulator, it’s sent back to the compressor where the process begins all over again. Since the refrigerant is constantly recycled, your vehicle can always cool down air when necessary regardless of outside factors.

Taking Care of Your Car’s A/C System

Here’s a quick look at two things commonly done by technicians to ensure the proper functioning of your car’s A/C:

A/C flush

A flush is typically done whenever a compressor fails or during routine maintenance of the car’s A/C systems. A flush is a relatively simple procedure in which a flushing liquid is forced through the entirety of the A/C’s components. (minus the compressor and a few other parts) to properly clean out any debris that may have accumulated over time. As well as the small metal shards typically present after a compressor failure.

A/C vacuum

An A/C vacuum requires an adequately oiled AC vacuum pump and is used by technicians to remove air and water vapor, while the system is being worked on. While a flush is used to remove particulate matter from the system. The A/C vacuum is meant to remove any excess air that has made its way into the system over time.


That’s how your average car goes about regulating the temperature within your cabin. It’s a very efficient and effective way of accomplishing this task as long as the passageways are kept free of debris. The tiniest amount of excess dirt can block the passageways within and lead to catastrophic failure.

Most of the time, the only major issue people will face with their systems is a failed compressor. Which can be replaced fairly easily. Our ability to rapidly heat or cool air is one of the greatest quality of life improvements we’ve put into our automobiles. Hopefully, this article was informative in helping you understand exactly how we managed to accomplish that feat.

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