How Does Car Air Conditioning Work? (AC Systems in Autos)

Remember the days you used to have to roll down the windows in your car and let the air flow through to get some relief from the heat? I don’t either. Car air conditioning has revolutionized the way we stay cool when we travel.

There’s a lot more that goes into developing your car’s climate control system than you may realize. So, how does car air-conditioning work? Let’s take a look in the guide below.

How Does Car Air Conditioning Work?

Your car’s AC system works by cycling refrigerant, converting it from a gas into a liquid, and then converting it back. At the end of the cycle, it’s in a cold gaseous state inside the evaporator, where outside air is blown over it, cooled, and then blown into the cabin. Let’s take a closer look.

The AC compressor sends gas to the next component of the car AC system, the condenser. The condenser captures the hot gas and transfers it out of the AC system. Air is flowing around the condenser, cooling the refrigerant as it passes through.

The receiver has an inlet point and an outlet point. The inlet takes inbound high-pressure liquid from the condenser and sends it through a series of filters to remove debris like dust, dirt, and metal particles. Then the refrigerant is then sent to the expansion valve via the outlet point.

An expansion valve controls how much refrigerant is allowed to continue through the AC system. This process reduces pressure and rapidly cools the refrigerant. An AC system with an orifice tube replaces the receiver dryer with an accumulator. The difference between an orifice tube and an expansion valve is that the former has a fixed opening. Now the refrigerant is nearly ready to cool your car, right after it goes through the evaporator.

The evaporator is similar to the condenser, containing lines that the refrigerant flows through. The evaporator absorbs heat, lowering the temperature to about 32-degrees. This boils the refrigerant back into a gaseous state, allowing it to absorb even more heat. The gas flows back into the AC compressor to start the process over again.

How Car AC Works

Why are Car Air Conditioners So Good?

Your vehicle’s air conditioning and heating system are some of the most important parts of your vehicle. It provides you and your passengers a comfortable environment to travel in. It will heat up your car in the winter, and in the summer, it will cool it down.

It’s not unusual for your windshield to fog up during the colder months, making it hard to see while you’re driving. Your air conditioning and heating system can remove the fog by defogging your windshield and windows.

Keeping your car cool during the warm season ensures safer driving. Discomfort caused by heat can create distractions and lead to risky situations. That means a functioning air conditioning system isn’t just a matter of comfort or convenience, but it’s a legitimate health concern. This is particularly true for elderly drivers, drivers with children, or anyone sensitive to heat.

Available Car AC Options

There are two types of air conditioning systems used in the automotive industry. Those two types are expansion valves and fixed orifice tubes. The main difference between them is the type of device used to lower the refrigerant pressure.

Expansion Valves

Expansion valves control the refrigerant flow in the refrigeration system in your car’s air conditioner. They facilitate the change of higher pressure of liquid refrigerant in the condensing unit to lower pressure gas refrigerant found in the evaporator.

The evaporator is the part of the system that operates under low pressure. The condenser is used to indicate the part of the system that operates under high pressure.

Fixed Orifice Tubes

Fixed orifice tube systems function the same way as the expansion valve system, apart from one component. Fixed orifice tube systems have a fixed orifice tube instead of an expansion valve. The fixed orifice tube works the same ways as the expansion valve, allowing a metered quantity of high-pressure liquid refrigerant into the evaporator.

Car AC Block Diagram

Common Signs of Faulty Car Air Conditioning

Knowing if your Air Conditioning is faulty isn’t as difficult as you thought. Most symptoms of a bad AC compressor are clear to see. Here are three of the most common symptoms of faulty air conditioning.

Your AC Doesn’t Blow Cold Air

The easiest symptom to recognize of a bad compressor is an AC unit not blowing cold air. Three things can keep your AC from blowing cold air. You could have a low level of the refrigerant, your refrigerant could be leaking, or your compressor could be going bad and needs to be replaced.

Loud Noises Coming From Your Air Conditioner

Loud noises when your AC turns on is another potential symptom of a bad AC compressor. If any interior components of the system break or the compressor’s internal bearings fail, all kinds of noises can be produced. The best thing to do here is to replace the entire AC compressor.

Water Leaks

Your AC system is designed to drain water out through the bottom of your car. The drains that facilitate this process can become blocked, causing water to back up and accumulate inside your vehicle.

Moisture that was supposed to be directed outside of your vehicle that gets backed up can spill out onto your passenger’s side floor. This is often the result of a clogged drain line or excess condensation.

What Can Cause Air Conditioning to Malfunction?

Refrigerant leaking – Most Common

One of the most common causes of a malfunctioning car air conditioner is a refrigerant leak. A refrigerant leak is often the result of rubber seals and hoses breaking down, allowing the refrigerant to escape.  

If you suspect a refrigerant leak, an automotive technician will use a refrigerant leak detector to identify the leak to begin repairs and recharge the system to once again blow cold air.

Condenser Issues – Somewhat Common

The condenser plays a vital role in your car’s air conditioning unit. The condenser takes the humid air from the air compressor and helps turn the air cool. If your air conditioning isn’t cooling as much, it could mean that you have a failing condenser. Typically, the only way to fix the issue is through replacement.

Compressor Issues – Somewhat Common

Your air conditioning uses a compressor to keep the air moving. If the compressor stops working, the refrigerant won’t move around and you will need to order a replacement compressor. Compressors typically go bad from not being used for long periods of time.

The best way to combat this issue is to run your A/C system on full blast for about 15 minutes every three weeks, regardless of the outside temperature.

Compressor Issues – Rare (clutch is not moving)

Your compressor may also run into problems if the clutch gets stuck. If it’s stuck in the on position, your air conditioning will run continuously. If it’s stuck in the off position, it will keep it from running at all. A mechanic will have to look at what’s causing the problem with your compressor.

People Also Ask (FAQ)

How to maintain the car air conditioning to keep it working well?

To keep your air conditioning running well, make sure to run it from time to time in the winter, keep your condenser clear, clean your AC regularly and make sure you keep water out of the inside of your system.

How do I know if my car AC needs recharging?

The most telltale sign that your car AC needs recharging is a noticeable loss in the system’s cooling capability. The air will stop blowing cold, or it might not blow at all.

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

Run your air conditioning at least once a week. It would be best if you even run your AC in the winter to maintain the refrigerant gas pressure.

How does air conditioning work in a hybrid and electric car?

Instead of using an engine to power an AC compressor, an electric/hybrid car uses electricity. For example, Tesla cars use a compressor similar to one found in a refrigerator.

How can I make my car AC colder?

To make your AC colder, you can get your AC gas refilled and replace the cabin filter. The new gas will cool the air, and the new cabin filter will allow the AC blower to have a free-flowing passage.

Can I start my car with the AC on?

You can start your car with the AC on without affecting your engine in any way. It doesn’t matter whether the AC is on or off before you start your car.


Fortunately, we don’t have to worry about rolling down our windows or relying on the shade to stay cool in our cars. And, we don’t have to wear extra layers in the winter to keep warm. Hopefully, this article gave you an idea of the inner workings of your car’s AC. What did you think? Did anything surprise you?

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.