Does AC Compressor Control Heat In Car?

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Driving in the summer heat can be both uncomfortable and distracting. In extreme conditions, you may suffer even heat exhaustion, impairing your driving ability. As you formulate ways to counter the heat, you may wonder if the AC compressor controls heat in the car. Here's what our research uncovered about the topic.

The AC compressor in your car contributes to heat control by influencing the refrigerant flow in the car's AC system. As the refrigerant circulates the AC loop, it draws hot air from the vehicle's cabin and releases cool air into the cabin.

There is a lot to learn about your car's AC compressor. Dive in to learn more about the role of the AC compressor in your automobile. We will also tackle signs to watch out for to detect a malfunctioning AC compressor and how best you can maintain the compressor to keep it in good condition. Without further ado, let's get right in.

How Your Car's AC Operates

Like most people, you probably do not understand how your AC works - you just want it to work. However, it is vital to understand what happens between the time you press the button (or turn the knob) and get cold air blowing in your car.

This knowledge will help you zero down on the problem if it malfunctions. 

Woman adjusting interior temperature while driving on the road

While most of us know that the AC helps to create a comfortable environment in the passenger cabin by cooling the air and maintaining comfortable humidity levels, we may be unfamiliar with other AC roles. These are:

  • It contributes to supplying clean air in the passenger cabin. This role is vital, especially in towns with high pollutant concentrations.
  • It can minimize fog on the windshield during winter or on rainy days.

The automobile's AC system contains the refrigerant in a closed loop. Here is a diagrammatic representation of the refrigerant's path in your car's AC system.

This refrigerant changes state depending on the pressure exerted on it and the temperature levels it is subjected to. The changes enable it to absorb and release heat at different stages as it cycles the loop.

The car AC is a modified and compressed version of your home's AC. We will look at its different parts and their contribution to keeping the conditions in the passenger cabin comfortable.

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The evaporator is located behind the AC vent on the car's dashboard. Warm air from the passenger compartment flows into the evaporator. 

The refrigerant flows into the evaporator as a liquid. However, as it absorbs heat from the air flowing from the passenger compartment, its temperature increases, and it changes into a gas.

As the refrigerant absorbs the heat, it chills the walls of the evaporator coils. The blower motor then blows the cool air into your passenger's compartment.

The refrigerant needs to release the heat to enable it to absorb more heat and maintain ideal temperatures in the car. So, the next stop for the low-pressure gas is the expansion valve.

Expansion Valve

Liquid refrigerant can damage your AC's compressor since it cannot compress a liquid. The liquified refrigerant can ruin the valve structure within the compressor or reduce the crankcase's oil effectiveness as a lubricant. 

To protect the compressor from damage, automobile manufacturers install the expansion valve between the evaporator and the compressor.

Any refrigerant still in liquid form is converted to vapor in the expansion valve. Since the vapor retains its low pressure, it flows into the compressor as a low-pressure, high-temperature vapor.


The compressor exerts pressure on the low-pressure, high-temperature gas transforming it into a high-pressure, high-temperature vapor. This high pressure enables the refrigerant to keep circulating the loop.


The high-temperature, high-pressure gas in the compressor flows into the condenser. The condenser has fans that create convection currents, resulting in the refrigerant cooling down. As the gas loses heat, it converts into a liquid. 

This refrigerant leaves the condenser as a low-temperature, high-pressure gas. It then flows into the receiver-dryer before it flows into the expansion valve. 


The receiver-dryer is often sandwiched between the condenser and the expansion valve. But you can find it attached to the condenser in some car AC models.

As the refrigerant flows through the receiver-dryer, it retains its temperature and pressure levels. AC manufacturers install the receiver-dryer to serve these roles:

  • As a receiver, it stores any refrigerant and oil not in use during the AC's operation, for example, on a cool day when you barely need to use the AC.
  • As a dryer, it contains a desiccant that absorbs moisture inside the AC system. Moisture within the system can cause corrosion or result in the reduced effectiveness of the compressor's lubricating grease.
  • Some receiver dryers have filters that trap unwanted substances within the AC system.

The refrigerant flows from the condenser through the receiver-dryer into the expansion valve. It is in the expansion valve that the refrigerant releases pressure to become a low-pressure, low-temperature liquid. Next, the liquified refrigerant flows into the evaporator, thus starting a new cooling cycle.

As we have seen, the refrigerant passes through the expansion valve twice per cooling cycle - first, as it flows from the evaporator to the compressor and from the condenser back to the evaporator. 

How to Identify a Defective AC Compressor

The AC compressor is often referred to as the heart of air conditioning in your car since it pumps the refrigerant through its entire cycle. Therefore, the AC may fail to perform its duties when the compressor malfunctions.

Here are some pointers to guide you in identifying a defective AC compressor:

AC Fails to Cool the Passenger Cabin

One of the first indicators of a defective compressor is when the AC blows hot air through the vents. That said, the hot air may also be due to inadequate refrigerant in the AC system or a faulty electrical system in your vehicle.

Noise When You Run The AC

Defective internal components such as a seizing shaft or a faulty clutch can result in odd noise every time you crank the AC on. Furthermore, if the compressor parts lack sufficient lubrication, they can rub against each other, thus generating noise.

There are other suspects for a noisy engine compartment, such as a whining power steering pump or worn-out brake pads. So, if you detect any noise, turn off the AC and then back on while listening for the noise to determine whether the AC compressor is at fault.

AC Compressor Clutch Fails to Engage

The engine's crankshaft powers the compressor to enable its operations. For this reason, the compressor has a clutch that engages and disengages the engine on a need basis. 

If you turn on the AC, but the clutch fails to connect to the engine or has a stuck pulley, the compressor is faulty.

If you notice any of these signs, it is best to take your vehicle to the repair shop - a mechanic can inspect it, determine the damage extent, and resolve the issue, thus restoring AC functionality.

Read this article to discover: Can You Replace Just The Clutch On An AC Compressor? Should You?

How to Maintain an AC Compressor

Proper maintenance can keep the AC in good working condition for about 8 to 15 years. Here are some tips to guide you in maintaining your vehicle's AC compressor so you can get the most out of its useful life.

How To Maintain AC Compressor. Does AC Compressor Control Heat In Car

Inspect for Leaking Refrigerant

Refrigerant leaks can result in premature compressor failure since the compressor overworks to keep your passenger cabin cool. 

Please read this article to learn more: Will Low Freon Damage A Compressor?

Refrigerants pose various risks that include - but are not limited to - physical hazards, toxicity, or flammability. So, it is best to leave the inspection and refrigerant recharge to the care of certified refrigerant handlers.

It is ideal to schedule the inspection and recharge every 2-3 years. The refrigerant handler should begin by eliminating any channels for refrigerant loss before refilling it to avoid premature refrigerant depletion. 


Without adequate lubrication, the moveable compressor parts experience heightened wear and tear levels and break down more often. Furthermore, friction generates heat which may cause the system to overheat. 

It is best to add a few compressor oil ounces when recharging the refrigerant to ensure that the compressor remains well-lubricated.

See this compressor oil on Amazon.

Change Filters and the Desiccant

When dirt accumulates on the filters in the AC system, it hinders proper air circulation. In addition, dirty filters can also block oil and refrigerant flow through the receiver-dryer.

The desiccant has a moisture concentration beyond which it cannot absorb more humidity, thus losing its effectiveness. 

Regularly changing the filters and desiccant ensures that the AC system operates efficiently.

Run the AC Regularly

Running the AC at least once weekly, for about 10 minutes (even during winter), is ideal. This practice aids in maintaining the refrigerant pressure levels as it passes through the compressor.

Furthermore, running the AC prevents the compressor from wasting away as dust and debris accumulate when you fail to run the AC for a long time. You may also encounter refrigerant loss if you fail to run the AC for a long time.

Running the AC also helps eliminate excessive moisture in the car, which may lead to mildew growth or unpleasant odors. 

Regular Service

When you take your vehicle to the service center regularly, the mechanics can detect any malfunctions and repair them before the AC compressor fails prematurely.

By servicing your vehicle regularly, you save time and money, avoiding lengthy downtimes if the compressor breaks down and saving money that you would otherwise spend on costly repairs.

In addition, regular service offers a level of confidence that all the vehicle components are working as they should. Consequently, you can be sure that your car is safe for you and those inside.

Air conditioning button inside a car. Does AC Compressor Control Heat In Car

Wrapping Up

We hope the information in this post will guide you in taking care of the AC compressor and identifying a malfunctioning compressor since it is vital in controlling heat in the car.

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