How AC compressor works

How AC compressor works

Car air conditioning basics ➤ How a car ac works ☝

Have you ever found yourself stuck in traffic on a hot afternoon? This is the time you realize there is something wrong with your air conditioning. You might never have given it a thought before. But it is time you may want to have a look. And we are going to share with you in this article.

Air conditioning is simply the “conditions” of the air in the car. There is a lot that goes on, in that it does not only cool it down, it also reduces the moisture content. These air conditions work  the same way whether in a building or inside the vehicle. If you have an air conditioner in your house, then you know how it all works.

Even refrigeration, or a freezer, is in a way an air conditioner.  There are so many areas covered in air conditioning. But for now, we shall stick on how a car air conditioner works.


Car air conditioning basics

Did you know that you reduce the number of miles per gallon when you turn on the AC? Well, most car owners never realize this. Energy is needed to remove the moisture and hear from the air inside your vehicle’s cabin. This energy comes from petrol consumption from the extra load imposed on the engine.

The basic principle of a working AC involves evaporation and condensation, and, compression and expansion. This is known as thermodynamics to scientists.  Let us try to break this down for better understanding.


Try putting some spirit at the back of your hand and rub a little. You will immediately start to feel cold in the area. This is because of evaporation.  The spirits at the back of your hand starts evaporating. This process takes away the heat from your skin to leave you feeling cold.


Sometime you have noticed steaming glasses when someone walks into a take away from cold. This is because of condensation. The take-away has moist air, which cools as it hits the cold surface of the glasses. This air does not have enough capacity to hold the moisture, which cause it to condense in the process. It becomes water and rolls off the glasses.

Heat of compression

Have you ever pumped air into a bicycle tire? Touch the end the pump and feel how it gets hot. As you push the pump, the air inside is compressed. This causes it to move close to each other a rub against each other, creating friction which converts into heat.

Cooling by expansion

Using a deodorant feels cold on the skin. This is because the propellant has just expanded in volume rapidly.

That is it with the basics. The most important question is how all these is applicable in air conditioning. These aspects are the physic s behind the working of a car AC.  There are hard tubing and flexible hoses in the car air conditioning system that connects all other components of the AC in your car.

This brings us to the components of the AC, which include:  The AC compressor, the condenser, receiver-dryer, expansion valve and the evaporator.


How a car ac works

A refrigerant is the fluid that passes around the whole system. This fluid can evaporate at a low temperature, and condense at higher pressure. Before technology too over, R-12 was the main refrigerant. It was used in many cars but later discovered to have an effect on the Ozone layer. From 1996, the uses of a new non-CFC fluid called R-134A came into use as a more friendly option.

Here is a break-down of different components and how they work:


The automotive ac system has a compressor which is the main work force in an AC system. It is the main part, powered by the drive belt connect to the crankshaft of the engine.

When the aircon is on, this component pumps the refrigerant vapor to the condenser. This is pumped at a high pressure. It is important for the pressure to be high enough to achieve proper cooling upon hitting the condenser.

The condenser

Another very important component of the automobile air conditioning system is the condenser. If you refer to the example we have shared above, you can almost tell what this part is for.

High-pressure refrigerant vapor enters the condenser from the compressor. Here is where the vapor is converted into a liquid.

The condenser is mounted in-front of the radiator and looks almost like the radiator. Those who are not familiar with the two components can easily get confused.

It is called a condenser because it condenses the vapor into a liquid. The high pressure driving in it plays the major role in this conversion. There is a great deal of heat involved, which is removed by the air flowing on the outside of the condenser.

The receiver

Now the vapor which has been turned into a liquid moves to the receiver-dryer. The receiver-dryer is a small reservoir vessel for the liquid refrigerant. It serves the purpose of cleaning the refrigerant.

Sometime moisture may have leaked into the refrigerant. This moisture can make the AC to perform abnormally. This is where the dryer-receiver comes in to remove anything unwanted from the liquid. Moisture is dangerous and can cause havoc. Ice crystals for instance may cause blockages and lead to mechanical damages.

The expansion valve

From the receiver-dryer, the pressurized refrigerant flow directly into the expansion valve. At the name suggest, this component enables the expansion of thee refrigerant.

Since the liquid is flowing at a high pressure, it cannot expand at this state. The expansion valve there removes the pressure. The liquid is heading to another component where it is to be converted back into vapor.

At this point the refrigerant is still cold. Only that now there is less pressure and it come move much easier. Remember that what we are looking for is a cooler environment inside the cabin. This liquid is making it so.

The evaporator

The refrigerant with less pressure can now move into the evaporator. This is another auto part that resembles a radiator. It is connected with tubes and fins and usually located inside the passenger compartment. It can be seen behind the fascia above the footwear.

The vaporizer vaporizes the cold low-pressure refrigerant, absorbing the heat from the air in the passenger compartment. This compartment is fitted with blower fans which pushed air over the evaporator enabling circulation of cold air. The evaporator has an ‘air side’ on which moisture is reduced.


The low-pressure air refrigerant vapor is drawn back into the compressor. This starts another compression cycle which runs continuously. The expansion valve plays another role or regulating the air.

This process is quite easy. Even a simple diagram can be used to explain how the mechanism works. All AC work on the same principle. There may be slight variations in the components, depending on the model of the car, but that does not affect the process.

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