Car AC System Parts and Functions, With Short Descriptions

Suppose you live in places like Key West Florida, Maima, Tucson Arizona, or Las Vegas. In that case, you’ll agree that there’s no pleasure in driving without a good working air conditioner, especially during summer. Therefore, you have to always ensure the AC works properly before we enter next summer.

Rx mechanic vetted auto service writer will outline car AC system parts with their functions and short descriptions. Like several car systems, the complete AC system for cars consists of several components that work in unison.

By the time you finish reading this article, you can point out different AC parts and explain how it works in correlation with other AC components. But first, let’s look at types of car AC.

complete ac system for car

Types of car AC systems

We have two main types of air conditioning systems. Technically, these two systems work the same way. The only difference is the component used in lowering refrigerant pressure. They include;

Thermal expansion valve system

This air conditioning system uses a thermal expansion valve to drop the refrigerant pressure. The thermal expansion valve is a variable control valve mounted close to the evaporator.

Fixed-Orifice tube system

The fixed-orifice tube AC system, commonly called the compressor cycling orifice tube system, is the second type of car air conditioning system. This system uses a fixed orifice with an opening of fixed size instead of a variable control valve like the thermal expansion valve system.

Here, the cycling on and off the compressor controls the refrigerant flow. The system also has an accumulator on the AC line that connects the compressor to the evaporator.

At this point, you’ll no longer ask what are the two types of automotive air conditioning systems?. We’ve explained them. Now, let’s explore the various car air conditioner parts and functions.

Car AC System Parts


car ac compressor

The car air conditioning compressor is the power unit. It is a pump with a pulley attached and connected to the engine pulley via a serpentine belt. As the engine rotates, the compressor pulley spins along. It is also responsible for distributing the refrigerant or freon to other car ac system components.

The AC compressor has a clutch unit that compresses the low-pressure refrigerant into high-pressure gas. The primary functions of the air conditioner compressor are

  • Compressing low-pressure refrigerant to high-pressure gas
  • Controlling temperature changes
  • Transporting air to the condenser.



The condenser is another essential AC system component that assists the compressor. It has the shape of a cooling system radiator and does the same cooling job as the radiator. The only difference is that the radiator cools engine coolant, while the condenser cools high-temperature refrigerant from the compressor.

Once it receives the high-temperature freon or refrigerant from the compressor, it radiates the heat and changes it from gas to liquid.

Receiver Drier

The receiver driver is another critical air conditioning part located between the expansion valve and the condenser. The cooled refrigerant traveling through the high-pressure lines pass through the drier inlet port.

The drier has a desiccant unit that filters and removes dirt and debris from the liquid before sending it to the expansion valve. By this, it ensures the liquid is safe and will not clog the thermal expansion valve or orifice tube.

Thermal expansion valve

Thermal expansion valve

A thermal expansion valve or orifice tube is a throttling device that expands high-pressure gas. It adjusts the refrigerant flow into the evaporator to suit the heat load in the enclosure. This way, it meters and controls the difference between the superheat and current refrigerant temperature at the evaporator outlet.



The evaporator is one of the essential AC system components. It is also one of the AC system parts you’ll hardly notice that exists because it is mounted behind the dash. The evaporator absorbs heat from the AC refrigerant, removes humidity from the air, and circulates the cooled air inside the cabin with the help of the blower motor.

Blower motor

AC Blower motor

The blower motor is an essential HVAC system component that does the final air conditioning task. Its primary function is the blow air against the evaporator to send the cooled air into the cabin through air vents. It is a heating and cooling system that ensures you get the required air inside the cabin.

Car AC refrigerant or freon

Car AC refrigerant

This is self-explanatory. The AC refrigerant is a compound that absorbs heat. It travels through several car air conditioning system parts, changing from gas to liquid states. As it travels to other parts, it absorbs heat to releas it along the journey to bring cold air into your cabin.

While refrigerant or freon is essential for an AC to blow cozy air, using the correct AC refrigerant for your car is more important. Here are the three common types of ac refrigerants.

Freon (R12): Used on older vehicles produced before 1994

R134a or HFC134a: Used on newer model cars built from 1994 to 2014

HFC1234yf or R-1234a Used in new model cars manufactured from 2014 to date.

However, it is crucial to stick to the manufacturer’s recommendations when recharging your car AC, especially regarding the refrigerant type and the compressor oil. Therefore, always find out the recommended refrigerant and oil before contacting your automotive air conditioning parts suppliers.


Q: What are the 5 major components of a fixed orifice system in an automotive air conditioning system?

The air conditioning system consists of several components to work in unison to ensure you receive the desired cooled air inside the cabin. However, the five major AC components in a fixed orifice system are the compressor, condenser, receiver/dryer, orifice tube, and evaporator.

In any case, kindly note that the difference between a fixed orifice and a thermal expansion AC system is that the Fixed orifice system uses a fixed orifice tube in place of a thermal expansion valve. Besides this, both air conditioning systems use the same system components.

Q: Will an AC motor run without a capacitor?

A permanent-split AC motor needs a capacitor in its circuit to generate a starting torque. And a single-phase induction ac motor can not run without a capacitor. However, some AC motors can run without capacitors. Although, I don’t advise you to run your AC motor without a capacitor because the unit will run hot and degrade the stator winding insulation.

Q: How many capacitors are in an AC unit?

Ac units usually have two single capacitors or one dual capacitor on the outdoor unit, depending on your air conditioning system design. In AC systems with two capacitors, one controls the starting, while the other is for the running.

The run capacitors are the most common. They save the electric flow needed to keep the air conditioning motor running. On the other hand, the start capacitor only provides the necessary power to start the air conditioner.

Final Words

Having gone through different car AC system parts and their functions, you can identify each part in your vehicle and what they do. Besides, we’ve seen the two different types of ac systems. The two air conditioning systems work with the same components in the same way.

The only difference is that the expansion system uses an active device (thermal expansion valve) that regulates refrigerant flow to the evaporator, depending on the evaporator’s temperature. In contrast, the orifice system uses an orifice tube, a simple fixed device with no moving parts that regulate the refrigerant going to the evaporator.


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