Informational Guide

How Does a Car AC Work?

We look at the automotive HVAC system, explaining the types, operations and problems associated.

On a hot day, you take your car air conditioning for granted. It’s expected to work and cool you off, but you never really consider - how does car air conditioning work?

We look at the automotive HVAC system, explaining the types and operation.

The expansion valve system

This complex AC system uses a valve to regulate refrigerant flow. A rod opens or closes to a varying height based on the demand of the system, which creates a drop in temperature as long as the system contains the right amount of refrigerant.

tube system

The fixed orifice tube system

In this system, an orifice tube is used, which is a fixed device without moving parts. There is no expansion valve, so the flow of refrigerant isn’t restricted the same way.

This design relies on filters to remove debris, but these can sometimes get clogged.

How Does Car Air Conditioning Work?

When you turn on the cooling in your vehicle, it shoots out cold air, but how does a car air conditioning system work? There are many different components involved and stages to cooling the air. Here are the main parts.


How does a car air conditioning compressor work? This is the most important part because it is responsible for pressurizing the refrigerant and sensing any temperature changes. It also monitors the output and moves refrigerant into the condenser


The condenser reduces the temperature and pressure of any hot gasses coming with the refrigerant. It’s also needed to move the liquid refrigerant to the dryer/receiver or accumulator.

Receiver/drier or accumulator

If your system has a thermal expansion valve, it also has a receiver/dryer. Otherwise, the accumulator is found in systems with the orifice tube. The receiver/dryer separates gas from the liquid and takes any moisture out. In comparison, the accumulator controls how much refrigerant moves to the evaporator and also removes moisture.

Expansion valve or orifice tube

When you look at our “how does car air conditioning work diagram” above, you see that both of these parts are found between the condenser and evaporator. They are responsible for regulating the pressure and temperature of the system to ensure the right amount of refrigerant is used.


The reason you feel the cold air is because of the evaporator. It’s located directly behind the dashboard and cools the air with refrigerant right before blowing into the cabin.

The AC system in your vehicle is complicated and runs on the engine, so you might find yourself using more fuel while running the air conditioning. However, you can use just as much fuel, creating a drag from having your windows down on the highway.

Benefits of Having AC in your Car

There are many benefits to having a properly working AC system in the car, besides being comfortable. For example, if the driver is too hot or too cold, it can become distracting, which could lead to an accident. 

Furthermore, the car interior remains in better condition without the debris of the outside world flying around and when the humidity is removed through air conditioning.

Many people don’t realize that the defrost function also uses the AC system to run. Without it, you would have frosty, foggy windows when the temperature takes a dive.

Common Signs of Faulty Car Air Conditioning

When the AC system starts to fail, you often know it. However, with so many working parts, it can be tough to determine what is going wrong. Look for these common systems that your AC needs attention.

  • Air conditioning isn’t blowing as cold as it once did
  • Moisture is leaking into the cabin
  • Strange odors are coming from the car vents
  • A loud noise occurs whenever the air conditioning switches on

What Can Cause Air Conditioning to Malfunction?

Refrigerant leaks

While a leak can happen anywhere, it’s often difficult to figure out where it happened. Check the hose connections first to look for oil substances building up.

Blocked condenser

The condenser cools the hot refrigerant after compression, but if there is a blockage from road debris, it cannot perform this task, making it impossible to cool the cabin.

Electrical issues

The electrical system is integral to the AC system, but it’s also hard to diagnose. If any damaged wires or connections occur anywhere in the system, you might suffer in the heat. 

Bad condenser

If you’ve looked at the condenser, but nothing is blocking it, then it could be broken. Sometimes, the condenser gets punctured from debris on the road as it sits just through the grille of your vehicle.

Compressor clutch is not moving

The compressor keeps the system running at all times. If the clutch is broken, the refrigerant can no longer circulate through the system.

Defective cooling fans

Additionally, the cooling fan could be broken, leading you to only get hot air from the system. Cracks in the fan or blown fuses can cause this problem.

5 Car Air Conditioning Maintenance Tips (From a Mechanic)

1. Run defrost mode for about 5 to 10 minutes

By running the AC on Defrost, you prevent mildew from building up in the system.

2. Use your air conditioner in winter as well

You want to run the air conditioning for ten minutes every week, no matter what the weather conditions are. This keeps the right amount of pressure in the system, so it continues to work.

3. Recharge your air conditioning system

Every two years, you should have the system recharged with lubricant and gas.

4. Get a full air conditioning service

You want to get the system checked out regularly.  A full inspection can be performed, plus a recharge, which should cost you around $150.

5. How to keep moisture out of your AC system?

By running the AC system regularly, you help to remove condensation, which can kill the system components.

People Also Ask (FAQs)

How do I know if my car AC needs recharging?

The air in your cabin will be blowing out at the same force, but you will notice that the temperature is warmer than usual.

How often should you use the air conditioner in your car?

Aside from using it when you need it, you must run the air conditioning for at least ten minutes a week, year-round. This keeps the condensation at a minimum and ensures the proper pressure.

How does air conditioning work in a hybrid car?

In many hybrid cars, the air conditioning compressor is connected directly to the battery, allowing you to run the air when the engine isn’t even on.

How does air conditioning work on electric cars?

Just like with the hybrid system, an electric car uses the battery to power up the AC system. Because of this design, you might be able to get cold air out of your EV without the engine running.

Is AC in cars only for cold air?

No, the air conditioning not only cools the air but also dehumidifies it as well. That’s why the AC system is used to run the defrost on the windows.

How can I make my car AC colder?

The best way to cool off the car is to ensure the refrigerant levels are correct. If you keep having to charge your system, there might be a leak that needs to be repaired.

Is it bad to start your car with AC on?

Yes, you can run your AC with your car on. However, you are using fuel and getting 0 miles per gallon while you sit there.


Now, you have a better understanding of how the car’s AC system works. Because there are so many vital parts involved, it’s essential that you maintain the system to ensure you always have cold air when you need it.