What does the Air Compressor in a Car do?

Posted on: April 23, 2020

what does the air compressor in a car do

What Does an Air Compressor in a Car Do?

Air compressors have made life easier for people on countless fronts since the early days of automotive assembly. As technologies advanced, productions along assembly lines sped up as cars became cheaper and easier to produce, which allowed automakers to sell their vehicles to consumers at lower prices. One of the greatest innovations during this time was air conditioning, which made life easier for people in the humid depths of summer months.

A/C systems were soon incorporated into automobiles, which allowed families to commute and embark on vacations in greater comfort because temperatures inside of passenger compartments could now be lowered by at least 20° from the outdoor weather. So what does a car’s air compressor do? The air compressor makes the whole A/C process possible in vehicles.


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How Does the Air Compressor Cool Your Car?

When spring and summer temperatures start to boil along the highways and congested roads, there’s nothing more refreshing than the cool blast of air conditioning from the vents of a car, truck or van. In the heat of 85°-plus temperatures, that icy A/C breeze can feel like the ultimate relief from the virtual oven outside.

Despite the cool feeling, however, there’s no actual ice involved in the A/C process. Those icy gusts you’re experiencing are actually the result of hot gases being removed from the humid air. It’s a multi-step, thermodynamic process that’s all made possible by the power of air compression.

Whether you’re the driver or passenger, you take control of the car’s air compressor the moment you push the A/C button. By doing so, you’ve activated the compressor to compress and hike the temperature of the refrigerant. After activation, the refrigerant is then sent through the condenser, where the heat is lost. Next, the refrigerant goes through the dryer and is purified of contaminants. Once purified, the refrigerant is stripped of its pressure after it passes through the expansion valve. The final step is traveling through the evaporator inside the dashboard, and the refrigerant is rendered super cold and moisture free. The gusts of cold air you feel are the result of the motor’s blower pumping air through this newly cold refrigerant and out through the blowers.

air compressor in a car

How Long Do A/C Air Compressors Last?

To the vast majority of drivers, the functions that take place under the hood of a car are seldom considered — unless a strange sound is heard or a warning light flashes. As a function of vehicles that’s used primarily during warmer months, the air conditioning compressor doesn’t quite face the same amount of year-round wear and tear as the brakes and clutch, but it does have its share of vulnerabilities. After all, it’s the drive belt of the engine that sets the whole A/C process into motion.

While it’s hard to determine the amount of time a given car part will function to its maximum abilities, certain factors might indicate the likely lifespan of an A/C air compressor. The foremost factor is the vehicle’s age. While new vehicles tend to be equipped with more durable compressors, the toll of mileage can affect any of the internal parts. If the compressor bears repeated undue stress over time, it could slowly lose its ability to send cool air into the passenger compartment.

While the A/C compressor can benefit from the relative lack of wear during winter months, it can also stagnate if left to hibernate during this time. Therefore, it’s best to activate the A/C for at least 10 minutes every 30 days between November and February to ensure it doesn’t take a permanent rest. Granted, the functions in question here are not limited to the A/C in all vehicles. In some cars, the compressor is also utilized to offer heat and ventilation, both of which tend to be used primarily between late fall and early spring.

car air compressors

If you or a prior owner has already had the A/C air compressor replaced, its life expectancy could be shorter than the original unit that came with the vehicle as it rolled off the assembly line. Online, warranties of 12 to 24 months are typically offered by specialists of auto parts, but an A/C air compressor will usually outlast this timeframe if utilized properly.

How Often Should an A/C Air Compressor Undergo Maintenance?

The litmus test for a working A/C system is whether or not it keeps you and your passengers sufficiently cool when it’s hot outside. If a few minutes of breeze actually makes your car feel too cold — despite temperatures of 95° or more outside — then your A/C isn’t due for maintenance and probably won’t be for the foreseeable future. As the saying goes, if it isn’t broken, don’t fix it — the money can be saved or allocated to other areas of car repair.

So when should you take your vehicle in for A/C maintenance? If coldness is either slight or nonexistent in the air coming through the vents, it’s likely due to problems with the system. Depending on the extent of the problem, you’ll either need a recharge or an outright replacement of the A/C air compressor. For most cars, a recharge is needed every few years, but replacements can be avoided for the average span of ownership of most vehicles as long as due care is taken for the A/C system.

In any case, when your vehicle’s A/C starts to lag, it’s time for an inspection. Considering the high-pressure functions that a compressor must perform in order to provide cooled air, the circuitry is complex and maintenance is usually best performed by skilled technicians.

What Is the Key Fluid in an A/C System?

If your A/C fails to deliver the coolness levels you’ve come to expect, it’s likely down to a low supply of refrigerant — the fluid that makes cold air from hot air. What exactly are the elements that comprise this fluid? For that, a bit of history is in order.

what do air compressors in cars do

Traditionally referred to by the antiquated DuPont trademark Freon, refrigerant comes in three forms that have appeared in succession since the dawn of air conditioning: R-12, R-134A and HFO-1234yf. Much like oil and antifreeze, refrigerant is one of the fluids that facilitates a vital function in most vehicles.

Technically, the only actual Freon was R-11, which was one of the most common chlorofluorocarbon (CFM) fluids in use up until 1996, when CFM was banned in the United States due to its impact on the ozone. Subsequently, automakers replaced R-11 with the non-CFM fluid R-134A, which scientists developed as a somewhat eco-friendlier though still chemically-laden refrigerant. In 2013, however, the auto industry initiated another change, this time to HFO-1234yf, which is believed to be the most environmentally sound refrigerant yet conceived. With this latest development, cars pose a smaller environmental threat in cases where the refrigerant leaks.

What Are the Components of an A/C System?

The majority of A/C systems comprise the following parts, which collectively function to make cold air appear inside of vehicles:


The air compressor is the heart of an A/C system. Without one, you’re left with simple blowing fans that do nothing more than suck the outside air and its atmospheric temperatures into your vehicle. Refrigerant is pressurized by the air compressor, which senses the temperature in your vehicle and makes desired changes when activated to do so from the center console. The air compressor itself is powered, like various other engine parts, by the serpentine belt. If the belt snaps, the A/C system won’t function, but neither will the car itself. Signs of an ailing compressor include strange noises, fluid leaks and inconsistent operability.

car air compressors


As the component responsible for converting hot gas into cold fluid, the condenser transforms air in a way that would never be possible with a conventional fan. In the majority of vehicles, the condenser is situated in front of the radiator. As such, it’s sometimes thought of as a miniature radiator. The condenser radiates the humid air that’s sucked into the air compressor. Then it depressurizes, cools and liquefies that air, finally sending it to the dryer. Signs of a malfunctioning condenser include fluid leaks, cracked tubes, eroded fins, clogs or insufficient coolness from the A/C vents.


On vehicles equipped with thermal expansion valves, the receiver safeguards the air compressor from dirt, moisture and other outside elements. As atmospheric air enters the A/C system, the receiver traps all the water, moisture and other impurities, which are filtered from the gas before it’s sent to the air compressor. Without this filtering, the A/C process wouldn’t work for two reasons:

  • The water would penetrate and damage the air compressor.
  • Moisture, when mixed with refrigerant, can unleash acidic contaminants into the system.

The filtering is accomplished with desiccants, the likes of which are also used in moisture-inhibiting packets — the kind that are included in the commercial cardboard boxes in which home electronics are sold and shipped. Signs of a lagging receiver include a lack of cold air once the A/C is activated or an inability of the defroster to clear up moisture-laden windows. A dryer needs to be replaced whenever dirt or moisture has been found to inhibit its operability or whenever the A/C system is accessed for repair work.


On vehicles equipped with orifice tubes instead of thermal expansion valves, an accumulator is used in lieu of a dryer. As with a dryer, the accumulator filters dirt and eliminates moisture from incoming air before it passes through the A/C system. The accumulator also restricts the level of refrigerant that gets into the evaporator and, in doing so, safeguards the air compressor from being penetrated by excess refrigerant. An accumulator needs to be replaced if dirt or condensation take their toll or in cases where the A/C is accessed for maintenance.

Expansion Valve

Along the A/C system, the condenser and evaporator are divided by the expansion valve, or the orifice tube in some vehicles. The valve/tube gauges the heat and pressure levels coming out of the condenser and accordingly regulates the refrigerant that enters the evaporator.

On certain tube-equipped vehicles, the orifice is enmeshed to filter impurities from the other components. If the A/C stops delivering sufficient amounts of cool air, it could be down to a faltering valve or tube, either of which could fail if clogged with debris or other impurities.


The evaporator is the component that cools the air and renders it moisture free. Whenever you turn on your A/C and feel a cooling satisfaction within seconds — regardless of whether it’s 100°-plus outside — it means your evaporator is in tip-top shape.

Situated behind the dashboard, the evaporator marks the last stop in the cooling process before the air enters the passenger compartment. The cooling itself occurs as the air passes through refrigerant in the evaporator, which simultaneously sucks atmospheric heat from within the car. As with other components within the system, the failure of the A/C to deliver sufficient coolness could be the result of a worn evaporator.


When the A/C button is pushed on the center console, the air compressor is activated by an electro-magnetic clutch. This enacts the pressurization of refrigerant for the condenser before it’s ultimately sent to the evaporator. Temperatures within the evaporator are gauged and regulated by the cycling clutch switch, which protects the core of the evaporator from freezing entirely. Signs of a failing clutch switch include freeze-up or insufficient coldness within the evaporator.

When the A/C system is being recharged, refrigerant enters in through the charge port, which is located on the large hose that’s situated close to the accumulator.

Air Compressors Make Life Easier

With the unique capabilities afforded by air compressors, today’s vehicles and assembly lines are equipped with functions that would otherwise be impossible. For nearly a century, Quincy Compressor has provided air compressors both large and small for virtually every type of pneumatic operation. While the process of compressing air is the same, Quincy’s compressor equipment is used in a variety of tough and demanding applications when efficient operation is paramount.

For huge factory operations, we’ve provided large stationary compressors that have made it possible to assemble everything from automobiles, boats and aircraft to furniture, electronics and kitchen appliances in only a fraction of the time it would take to assemble such things manually. In workshops and garages, our medium-sized and smaller compressors have given mechanics and craftsmen the ability to complete numerous tasks with far greater ease and efficiency than traditional tools would ever allow.

Across the United States and beyond, people with varying levels of mechanical skill have reaped the benefits of increased speed and physical ease that air-powered tools allow for when drilling holes, fastening bolts, inserting nails and applying paint on everything from walls to fixtures. Whether you specialize in auto repair, building construction, product assembly or personal crafts, an air compressor could be an asset to your productivity, regardless of the size and scope in which you operate. To learn more about Quincy’s compressors and pneumatic tools, check out our online products page and get in touch with our sales staff today.


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