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Air Conditioning in Cars: How Does It Work?


In the tropical climate of the Philippines, where temperatures often soar, functioning air conditioning in cars is more than just a luxury—it’s a necessity if you own one or ride one. 

Whether you’re navigating the bustling streets of Manila or embarking on a scenic drive through the countryside, having a cool, comfortable interior can make all the difference in your driving experience.

But have you ever wondered how exactly your car’s air conditioning system keeps you chilled even on the hottest of days? Let’s take a closer look at how they work.

The Basics: Understanding Car Air Conditioning Systems and Components

Air Conditioning in Cars: How Does It Work?

At its core, a car’s air conditioner system operates on the principles of refrigeration, utilizing a blend of mechanical and chemical processes to cool and dehumidify the draft inside the cabin. Here are the primary components of a car air conditioner system.


The compressor serves as the powerhouse of the car air conditioning system. Its primary function is to pressurize and circulate the refrigerant throughout the system. By compressing this, the vapor is drawn from the evaporator, and the compressor raises both its pressure and temperature significantly, preparing it for the cooling process ahead.

Think of the compressor as the car’s engine air conditioning system, providing the energy necessary to kick-start the refrigeration cycle and keep it running smoothly.


Situated at the front of the vehicle, the condenser plays a vital role in dissipating heat from the refrigerant. As the high-temperature refrigerant pressure enters the condenser coils, it encounters a flow of cooler outside draft.

This temperature differential facilitates the release of heat, causing it to condense into a high-pressure liquid. Essentially, the condenser acts as a mini radiator for the refrigerant, cooling it down and preparing it for the next stage of the cooling cycle.

Expansion Valve

The expansion valve, also known as the metering device or orifice tube, serves as a crucial control mechanism in the system of car air conditioners. Positioned between the condenser and the evaporator, the valve regulates the flow of refrigerant into the evaporator, ensuring that the correct amount enters the system.

By creating a pressure drop as the refrigerant enters through its narrow opening, the valve facilitates rapid expansion, causing it to cool significantly as it enters the evaporator.


Nestled inside the dashboard of your car, the evaporator is where the magic of cooling happens. Its primary function is to absorb heat from the draft drawn in from the cabin, effectively cooling it down in the process.

As the chilled refrigerant flows through the evaporator coils, windblown in by the blower fan passes over these coils, facilitating heat exchange. It then evaporates into a low-pressure gas, absorbing heat from the surroundings and effectively cooling it down before it’s circulated back into the cabin.

In essence, the evaporator serves as the cooling core of the system or car air conditioners, transforming warm, humid wind into a refreshing breeze.


At the heart of the refrigeration cycle lies the refrigerant, a specialized fluid that undergoes phase transitions to absorb and release heat. Typically a blend of chemicals with specific thermodynamic properties, refrigerant plays a crucial role in the cooling process.

As it circulates through the system, transitioning between liquid and gas phases, the refrigerant absorbs heat from the cabin air in the evaporator, releases heat to the outside in the condenser, and undergoes pressure changes controlled by the expansion valve. Its ability to facilitate heat transfer is what makes refrigerant indispensable in the air conditioning process.

Receiver Drier

The receiver drier is a crucial component of a car’s air conditioning (AC) system, primarily located on the high-pressure side of the system. Its main function is to filter and remove moisture and contaminants from the refrigerants before entering the valve and leaving the high-pressure side.

Where is the Air Conditioning System in a Car?

Air Conditioning in Cars: How Does It Work?

The car air conditioner system is a complex network of components strategically positioned throughout the vehicle to ensure energy-efficient cooling and comfort for passengers. At the heart of the system lies the compressor, typically located near the front of the engine bay, driven by the car’s engine crankshaft via a belt. This essential component pressurizes and circulates the refrigerant, setting the stage for the cooling capacity process.

Adjacent to the car’s radiator, behind the vehicle’s grille, sits the condenser. Here, the refrigerant undergoes a crucial phase of the cooling cycle, as it releases heat to the outside wind, transitioning from a high-pressure vapor to a high-pressure liquid. The valve, often found near the firewall between the engine compartment and the passenger cabin, acts as a gatekeeper, regulating the flow of refrigerant into the evaporator.

Inside the cabin, concealed within the dashboard or under the instrument panel on the passenger compartment side, lies the evaporator. Connected to the blower fan and air ducts, this component will absorb heat from the air, cooling it down as it passes over its coils. The refrigerant within the evaporator evaporates into a low-pressure gas, facilitating the heat exchange process and transforming the air into a refreshing breeze.

Throughout the vehicle, refrigerant lines snake their way, connecting the other components of the car air conditioning system and carrying the refrigerant between them. These lines are meticulously routed to optimize efficiency and minimize heat transfer.

Meanwhile, the blower fan, nestled inside the dashboard or beneath the glove compartment (passenger compartment), draws in the cooled air from the evaporator and circulates it back into the cabin through the vents.

Lastly, the controls for the air conditioning system are conveniently located on the dashboard, within easy reach of the driver and passengers. These controls allow for precise adjustment of the temperature, fan speed, and airflow direction, empowering occupants to tailor their comfort levels to their liking.

Together, these seamlessly integrated components work in harmony to provide cool, refreshing air, ensuring a comfortable driving experience even amidst the sweltering heat of the Philippine climate.

How Does Air Conditioning Work in a Car?

Air Conditioning in Cars: How Does It Work?

Now that we’re familiar with the main components, let’s delve into the intricate dance of the cooling cycle.


Imagine your car’s compressor clutch as the energetic heart of the AC system. When you start your vehicle and turn on the AC, the compressor springs into action, drawing in low-pressure, low-temperature refrigerant vapor from the evaporator. This vapor, having absorbed heat from the cabin, needs a boost to become effective at cooling.

The compressor’s job is to compress this refrigerant vapor, squeezing it tightly and raising both its pressure and temperature significantly. Think of it like a bicycle pump: as you push down on the handle, the air inside the pump becomes compressed, causing its temperature to rise. Similarly, the compressor compresses transforming it into a hot, high-pressure refrigerant gas ready for the next stage of the cooling cycle.


With its newfound energy, the high-pressure refrigerant gas journeys to the condenser, typically situated at the front of your vehicle where it can benefit from the flow of outside air. As the hot refrigerant gas enters the condenser coils, it encounters a stream of cooler air passing through the grille, facilitating the release of heat.

This exchange causes it to transform, changing from a high-pressure gas to a high-pressure liquid refrigerant. Much like a misty morning turning into dew on the grass, the refrigerant gas condenses, shedding its excess heat and preparing for the next phase of its cooling journey.

By the time it exits the condenser, it is now a high-pressure liquid refrigerant, primed and ready for the next step — a crucial one for the low-pressure side of the system.


The high-pressure liquid refrigerant now makes its way to the thermal expansion valve, a crucial component that serves as a gateway to the low-pressure side of the system. The thermal expansion valve is where the refrigerant encounters a sudden drop in pressure as it passes through the narrow valve opening, causing it to expand rapidly.

This expansion results in a significant decrease in both pressure and temperature, transforming the liquid into a chilly, low-pressure mixture of liquid and vapor. Picture the release of pressure when you open a bottle of soda—the rapid expansion creates a cooling effect, making the refrigerant even colder as it prepares to enter the evaporator.


As the now-cooled refrigerant enters the evaporator, located inside the dashboard of your car, it encounters air drawn in from the cabin by the blower fan. The evaporator’s coils are designed to maximize surface area, allowing for efficient heat exchange between the refrigerant and the incoming air.

As the air passes over the cold evaporator coils, heat from the air is absorbed by the refrigerant, causing it to evaporate into a low-pressure gas once again. This phase change— from liquid to gas—requires energy, which is extracted from the surrounding air, effectively cooling it down in the process. The cool air is then blown back into the cabin, providing you with that refreshing blast of coolness you crave on a hot day.


With the air now cooled and dehumidified, the cycle continues as the compressor draws in the low-pressure refrigerant vapor from the evaporator once more, restarting the process. This continuous circulation through the system ensures that your car’s interior remains consistently cool and comfortable, regardless of the temperature outside.

Which Type of AC is Used in Automobiles?

Air Conditioning in Cars: How Does It Work?

The most common type of system used in car air conditioners is the “Refrigerant Cycle Air Conditioning System,” which operates based on the principles of vapor compression refrigeration. This system utilizes a compressor, condenser, valve or orifice tube, evaporator, refrigerant lines, and a blower fan to cool and dehumidify the air inside the car’s cabin.

In this system, refrigerant undergoes a cycle of compression, condensation, expansion, and evaporation to remove heat from the warm air and release it outside the vehicle. The compressor pressurizes and circulates the refrigerant, while the condenser dissipates heat from the outside air. The expansion valve regulates the flow of refrigerant into the evaporator, where it absorbs heat from the warm and dry air, causing the refrigerant to evaporate into a low-pressure gas. Finally, the blower fan circulates the cold air flowing back into the cabin.

This type of system in air conditioners is preferred in automobiles due to its efficiency, reliability, and ability to provide rapid cooling even in hot climates like the Philippines. Additionally, advancements in technology have led to the development of more environmentally friendly refrigerants, further enhancing the sustainability of automotive air conditioning systems.

How Important is AC in a Car?

Air Conditioning in Cars: How Does It Work?

The importance of car air conditioning systems cannot be overstated, especially in regions with hot and humid climates like the Philippines. Here are several reasons why an AC system is crucial for vehicles.


An air conditioner provides a comfortable driving environment by cooling down the cabin and reducing humidity levels. This is particularly vital during hot and humid weather conditions, where driving without car air conditioning can lead to discomfort, fatigue, and even heat-related health issues.


Comfortable driving conditions are essential for safety on the road. Excessive heat inside the vehicle can lead to driver fatigue and distraction, impairing reaction times and increasing the risk of accidents. AC helps maintain a comfortable temperature, allowing drivers to stay focused and alert.


AC plays a role in promoting good health by reducing exposure to heat-related illnesses such as heat exhaustion and heatstroke. It also helps filter out airborne pollutants and allergens, improving air quality inside the cabin and minimizing respiratory issues for occupants.

Preservation of Interior

High temperatures and humidity levels can accelerate wear and tear on a car’s interior, causing materials to degrade and upholstery to fade. AC helps maintain a stable and comfortable environment, preserving the condition of the interior and protecting valuable belongings stored inside the vehicle.

Passenger Comfort

AC isn’t just important for the driver; it also enhances the comfort of passengers, ensuring an enjoyable journey for everyone on board. This is especially crucial for long trips or when traveling with children, elderly individuals, or pets who may be more sensitive to heat.

Resale Value

Aside from a vehicle running smoothly, a properly functioning AC system can positively impact the resale value of a vehicle and electric motor vehicles. Any vehicle owner would prioritize comfort features like AC when considering purchasing a car, and a well-maintained AC system can make a vehicle more attractive and desirable in the used car market. Consider your car sold if you have a properly maintained car air conditioning system.


For professionals who rely on their vehicles for work, such as delivery drivers or sales representatives, a comfortable cabin environment provided by AC can enhance productivity and job performance. It allows them to focus on their tasks without being distracted by discomfort or excessive heat.

How to Optimize the Efficiency of Automotive Air Conditioning Systems

Air Conditioning in Cars: How Does It Work?

While the basic principles of air conditioning remain constant, several factors can affect the efficiency and performance of your car’s AC system, particularly in the Philippine climate.


Regular maintenance is vital for ensuring the efficiency of your car’s AC system operation and ventilation system. One crucial aspect of maintenance is cleaning or replacing air filters. Over time, air filters can become clogged with dust, pollen, and other airborne particles, restricting airflow and reducing the system’s cooling effectiveness.

By regularly inspecting and cleaning or replacing air filters according to the manufacturer’s recommendations, you can ensure that air can flow freely through the system, maximizing cooling efficiency.

Another form of maintenance is making sure that refrigerant leaks are not happening. This is a common cause of car air conditioning problems. However, if a leak is present in a car’s air conditioner system, you may also choose to recharge the system with a new refrigerant.


Proper insulation of the cabin plays a crucial role in minimizing heat transfer from the outside environment, reducing the workload on the air conditioning system. Insulation materials, such as foam or fiberglass, help create a barrier between the interior of the vehicle and the outside air, preventing heat from entering and keeping the cabin cooler.

Solar Load

Parking in shaded areas or using sunshades can significantly reduce the solar load on your vehicle, which refers to the amount of heat absorbed from sunlight. When parked in direct sunlight, the interior of a car can quickly heat up, requiring the air conditioning system to work harder to cool it down. 

By parking in shaded areas whenever possible or using sunshades on the windshield and windows, you can help minimize the solar load on your vehicle, reducing the time and energy required for the air conditioning system to cool the interior.

Reducing the solar load not only helps improve the efficiency of the air conditioning system but also helps protect the interior of the vehicle from heat-related damage, such as fading or cracking of upholstery and dashboard materials.

Refrigerant Type

Choosing the right refrigerant for your air conditioning system is crucial for both performance and environmental considerations. Certain types are being phased out in the European Union due to higher global warming potential and safety reasons as they churn out more carbon dioxide than others.

With the ongoing transition to more environmentally friendly alternatives, selecting a refrigerant with low global warming potential (GWP) and ozone depletion potential (ODP) is becoming increasingly important.

Older refrigerants, such as R-134a, are being phased out due to their high GWP and ODP. In their place, newer refrigerants like R-1234yf are being adopted, which have a significantly lower environmental impact than the R-134a. These environmentally friendly refrigerants like the R-1234yf not only help mitigate climate change by reducing greenhouse gas emissions but also comply with regulations aimed at protecting the ozone layer.

When servicing or repairing your air conditioning system, it’s essential to use the appropriate refrigerant recommended by the manufacturer. Using the wrong refrigerant can not only affect system performance but also pose environmental and safety risks.


Air Conditioning in Cars: How Does It Work?

So, the next time you turn on your car’s air conditioning system and feel that welcome rush of cool air, take a moment to appreciate the intricate dance of mechanics and thermodynamics happening behind the scenes.

From compression to condensation, expansion to evaporation, each step plays a vital role in keeping you comfortable on the road, even amidst the sweltering heat of the Philippine climate.

JP Reyes

JP has been in the aircon industry for almost as long as he has been alive. As a child JP would help his tatay fix aircon units at their junk shop in Cavite. After graduating UP in the early 2000's, JP then started his own Aircon servicing business and within 5 years had 10 shops in 8 different cities. Fast forward to today and JP brings all his experience and expertise online to give readers trustworthy advice and reviews about Air-conditioning buying, servicing, cleaning and repair in the Philippines.

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