Driving around during scorching summer heats with your windows rolled down is unpleasant to say the least. Whether it’s the exhaust gases, hot air or noise pollution that is causing discomfort, rolling up the windows means no fresh air. That is, unless you turn on your A/C. Modern air conditioning units are a true game changer when it comes to maximizing driving comfort. But how does an A/C work? Join us as we break down this critical system and take a closer look at various A/C parts.

Article updated 04/08/21. Original publishing date 05/07/18

What is an A/C, and How Does It Work?

Air conditioners are systems designed to reduce ambient temperature, remove excess moisture, and provide fresh air to the environment by using a cooling cycle. The key part is the removal of humidity in addition to the reduction of ambient temperature.

The presence of excessive humidity makes breathing much harder than excessive temperature. A significant increase in humidity can slow down your reactions, which puts you and your passengers at unnecessary risk. For example, air with a temperature of 104 °F and 10% humidity is better than air at 86 °F and 80% humidity. Battling humidity is arguably a more important feature in certain parts of the world.

In many systems, there is also a function that allows for circulating of air inside the vehicle. It is one of the indispensable systems for the comfort of the driver and passengers. Today, air conditioning is used as a standard in most models of the cars being produced.

Vehicle air conditioning systems work on the same principle as refrigerator systems. In short, a magnetic clutch transfers the rotational movement from the engine to the air conditioner compressor via the accessory belt. The compressor pulley is constantly spinning when the engine is running, but the compressor itself is only activated when the magnetic clutch is pressed against the pulley. This is what happens when you press that A/C button.

At that moment, the A/C compressor starts driving the low pressure refrigerant from the evaporator part of the A/C system, turns it into a high temperature, high pressure gas and drives it into the condenser unit.

The condenser cools the gas into a high pressure liquid. From there, this highly pressurized liquid is sent into the receiver/dryer and further into the expansion valve. Once it leaves the expansion valve, it enters the evaporator where the liquid begins to boil, turning into low pressure gas. This process chills the evaporator. Then, a set of blower fans push air through the now cool evaporator, which is then sent into the passenger cabin.

Is My A/C Only for Cooling?

Although the A/C is used only for cooling in most vehicles, some air conditioners can also be used for heating purposes. In newer vehicles, even when the weather is very cold and the engine is still not warmed up enough, instant heating is provided by the air conditioner.

These kinds of mechanisms are called digital or automatic A/C systems.
A standard analog air conditioner is one that has only a cooling feature. To warm your car with an analog air conditioner, you should turn on the fans in the car and wait for the heat in the engine to be blown into the vehicle.

Automatic A/C Systems

Digital and automatic air conditioning systems have the added feature of stabilizing the temperature inside. With modern digital systems, it is now possible to keep the heat inside at the desired temperature.

It can also adjust the dryness or humidity without any user input. This feature also positively affects the fuel consumption as the A/C system isn’t constantly running.

Conventional air conditioners must be turned off 10 minutes before the car stops. Due to the heat generated, the water obtained from the steam accumulates, and when this water stays in place, it can lead to bad odors and even growth of fungi.

Automatic A/C systems manage their own operation, so the formation of bad odors is almost impossible. Due to this hygienic element, standard air conditioners must be operated regularly during the winter months.

Automatic systems may cause occasional nuisance with sensors or electrical parts, but they are definitely more practical.

Critical A/C Parts of Modern Air Conditioning Systems

Car A/C systems can be considered as split types since they are built using segmented units. The cooling capacity of the system is usually designed to match the volume of air inside your vehicle.

Here are the most critical A/C parts of modern air conditioning systems.

The Compressor

The compressor, commonly referred to as the heart of the A/C system, is a belt-driven pump connected to the engine. Your engine must be running for the compressor to work, as it takes its drive from the engine.

The pulley of the compressor will rotate because it is connected to the engine shaft using the accessory belt. When you press the air conditioner button, a magnetic clutch located inside the compressor pulley forms a hard connection between the accessory belt and the compressor itself. When the compressor is on, it pressurizes the refrigerant gas and sends it to the condenser.

The air conditioning system is divided into two sides, a high-pressure side and a low-pressure side; known as discharge and absorption. Since the compressor is basically a pump, it must have both an inlet and a discharge side. The inlet or suction side draws refrigerant gas from the evaporator outlet.

Condenser

The main task of the condenser is to liquefy the refrigerant gas. In most cases, it looks pretty much the same as the radiator in your car because the two have very a similar function. Hot compressed gases are cooled as they enter the top of the condenser.

The cooled gas exits the bottom of the condenser as a high-pressure liquid. The condenser is designed to dissipate heat. Usually positioned in front of the radiator, condensers must have good airflow while the system is running.

On rear-wheel-drive vehicles, this is often accomplished by making use of your engine’s existing cooling fan. In front-wheel drive vehicles, the airflow for the condenser is usually supplemented by one or more electric cooling fans.

Receiver Drier (Accumulator)

The main function of the receiver-dryer is to separate gas and liquid. The secondary purpose is to remove moisture and filter dirt. The top of the receiver-dryer is usually equipped with a sight glass meter.

This sight glass is also used to charge the system in many cases. You will find the receiver-dryer placed on the high side of A/C systems using a thermal expansion valve. The liquid refrigerant is needed for this type of metering valve.

Under normal operating conditions, vapor bubbles should not appear in the sight glass. The use of sight glass to charge the system is not recommended for R-134a systems because turbidity and oil leaving the refrigerant can be mixed with bubbles. Such an error can lead to a dangerous overcharge condition.

There are varieties of receiver-dryers and several different drying materials are used. There is a strainer and a desiccant inside the moisture trap filter. Here, water and dirt are separated from the cooling gas. The desiccant filter must be changed within certain periods.

Accumulators are used in systems that incorporate an orifice tube to measure refrigerants sent to the evaporator. It is used for storing excess liquid refrigerant and it is connected directly to the evaporator outlet. The liquid refrigerant entering a compressor can cause serious damage. Compressors are designed to compress the gas, not liquid.

Like receiver-dryers, accumulators remove debris and moisture from a system. It’s a good idea to replace your accumulator every time the system is opened for major repairs if moisture and/or dirt is involved.

Moisture is the number one enemy of your air conditioning system. If moisture mixes with the refrigerant, it forms a corrosive acid. When in doubt, it may be in your best interest to replace the accumulator or receiver in your System. While this may impact your budget in the short run, it benefits your air conditioning system in the long run.

Expansion Valve

Thermal expansion valve or TXV is a common refrigerant regulator. It can sense both temperature and pressure and is very effective in regulating the flow of refrigerant to the evaporator. Several variations of these valves are widely available.

The expansion valve is a needle valve. It opens and closes according to the temperature and provides the passage for the coolant. The refrigerant coming to the expansion valve will turn into a liquid and gas mixture as it passes through the expansion valve. The refrigerant liquid-gas mixture coming out of the expansion valve will enter the evaporator.

Such valves, although efficient, have some disadvantages over orifice tube systems. Like orifice tubes, these valves can become clogged with debris, but they also have small moving parts that can stick and fail due to corrosion.

In electric expansion valves, there is a temperature sensor at the outlet of the evaporator, the incoming coolant comes out by heating; The temperature sensor detects this amount of heating, sends a signal to the expansion valve, and the expansion valve increases or decreases the amount of refrigerant passing through.

The Evaporator

The evaporator acts as a heat absorption component in your A/C system. It plays a critical role in the cooling of the passenger cabin as it provides several functions. A secondary benefit is moisture removal.

As warmer air passes through the aluminum fins of the cooling evaporator coil, moisture in the air condenses on its surface. Dust and pollen passing through it stick to the wet surface and flow out. On humid days, you may have seen this as water dripping from under your vehicle. Rest assured that this is completely normal.

Temperature and pressure regulation devices are used to control the temperature. The ideal temperature of the evaporator is 32 °F or 0 °C. While there are many variants of the devices used, their main functions are the same; keep the pressure in the evaporator low and prevent the evaporator from freezing.

The refrigerant enters the bottom of the evaporator as a low-pressure liquid. Hot air passing through the evaporator blades causes the refrigerant to boil (refrigerants have very low boiling points). When the refrigerant starts to boil, it can absorb large amounts of heat. This heat is then removed from the vehicle while cool air gets blown into the passenger cabin.

Refrigerant and Oil

R134A refrigerant gas is used in auto air conditioning systems. The amount of refrigerant is very important for the performance and operation of the air conditioning system. Both, a large amount and a small amount affect the performance of the system.

A/C compressor oil is the liquid that lubricates the compressor while it is running. Special air conditioning oil (PAG=Poly-Alkylene-Glycol synthetic oil) should be used. It is necessary to check the amount of oil while checking the refrigerant during your air conditioner maintenance. Oil should be added if necessary.

A/C Pipes

Air conditioner pipes bring different flexibility and features depending on their design. Since they take air from the outside, the particles and plant pollen in the air coming from the outside accumulate in the pipes and parts in the air conditioning system over time. They can also get worn out after a while and start leaking.

You can fix a leak by covering the affected area. If the damaged pipe can be covered with a coating material, it is first cleaned and then covered with a coating material suitable for the type of pipe you have.

In other cases, a replacement of the affected pipe is necessary. It is important to find the right part for your vehicle because air conditioner pipes are usually produced specifically for vehicle models.

How to Find Quality A/C Parts?

After reading this article, you now know that the Air Conditioning unit of a car is made out of several components and each and every one of these is very important. If any of them fails, the system can not work correctly.

When your A/C doesn’t work, it will be very uncomfortable and sometimes even unsafe to drive your car. Always remember to use Genuine or OEM quality parts when you are replacing anything on your A/C system. We can help you get all the A/C Parts you need, just choose your vehicle’s make and model from our drop-down menu, and you’ll get a list containing all the original and OEM quality parts specifically made for your car.