Car Air Conditioning System: How Does It Work, and What’s Wrong With It?

You’re driving down the road. It’s a beautiful, hot day in the middle of July. Suddenly, the cool stream of air blowing into your face cuts out. Or, even worse, the air turns warm. Having a functioning air conditioning system in your car is a key part of a pleasant drive, no matter how far you’re going. There’s nothing worse than sitting in a stuffy, sweltering car as the sun beats down on you through the windows with no way to cool down the sticky air around you.

Car Air Conditioning System How Does It Work and Whats Wrong With It 2

While the car’s air conditioning isn’t considered as an immediate safety issue, it’s important for your comfort and eventually, being subject to boiling conditions may begin to affect your ability to focus on safe driving, so a broken air conditioner is definitely not something to ignore.

Plus, if there’s a leak or blown fuse, the issue could get worse and become dangerous over time.

If your car’s air conditioning system is faulty and you’re trying to get to the bottom of the issue, it’s crucial that you first understand how it works. In this guide, we will take you through all the major parts and components of a typical auto air conditioner, what they do individually, and how they work together to keep the airflow in your car nice and cool.

We will also highlight some of the issues that may arise with each of these parts, how to spot them, and how to fix them. Hopefully, you’ll be able to quickly and easily identify what has happened to your car’s air conditioning system, so you can take the next steps toward fixing it as soon as possible.

A basic rundown of how the system works

Before we go into the various parts that work together to keep the air in your car fresh and cool, it will be useful for you to understand the overall action being completed by these parts. Your car’s air conditioning system is basically a loop through which the refrigerant is pumped.

When the refrigerant goes through a pressure change, it either cools or warms. Refrigerant is a liquid mixture or substance designed to go through phase changes within the air conditioning loop. It’s typically made of fluorocarbons, but this type is currently being phased out in favor of more environmentally friendly alternatives.

Ammonia, sulfur dioxide, and hydrocarbons are also commonly used. By changing the amount of pressure being applied to this substance, the refrigerant will change either into a liquid or a gas, and in doing so, temperature also changes.

The four main parts of an air conditioning system

Here are the main components of your car`s air conditioner and what they do.

1. The compressor

The air conditioning compressor is driven by an electronic motor. Its job is to keep the refrigerant circulating through the whole system. It pulls in the refrigerant at low pressure, and by compressing it, it raises its temperature. Refrigerant leaves the compressor as a hot gas through tubes that lead to the condenser.

2. The condenser

The condenser looks like a small radiator. Air comes through the condenser to cool the refrigerant where it changes to a liquid because of its high pressure and dropping temperature.

3. Expansion valve or orifice tube

The next stage takes place in a tiny tube that holds the expansion valve, or in some cases, the orifice tube. As the name would suggest, the expansion valve allows the liquid to expand, removing the high pressure from the refrigerant. This reduction in pressure has the effect of cooling the refrigerant.

4. The evaporator

The evaporator is located in the airbox. It’s in the evaporator that the refrigerant phase changes for the last time, back into a gas.

Troubleshooting: What are the symptoms, and what do they mean?

If you think that one of the parts on your air conditioner might be malfunctioning and may need replacing or cleaning, here are some of the ways you can identify which part of the system is at fault. See if you have one of the following issues.

  1. Weak airflow

If you’ve noticed that the air temperature is still cool, but the amount of air coming out of your air conditioner seems lower than usual, several problems could be occurring. There may be a build-up of mold or mildew in the evaporator core, which can sometimes happen naturally over time. In this case, you’ll likely need to remove the evaporator, and have it professionally cleaned.

Another issue that could have happened is that something has become loose in the system, or one of the seals is leaking. This naturally means that some of the air and refrigerant is escaping out of the system and will also result in a weakened airflow.

2. Warmer air than usual

If you’re in that awful predicament of dealing with hot air blowing out of your air conditioning system, the issue most likely lies with a fault in the orifice tube section of the loop. When the expansion valve or orifice tube isn’t functioning, the refrigerant can’t expand, and therefore, can’t cool.

This is obviously a crucial part of the whole system and should be replaced immediately if it seems to be broken. If it’s possible to replace the orifice tube yourself, you might still need to enlist the help of a professional with the removing, and then later the recharging of the refrigerant, as this part of the process requires special equipment and tools.

If you’re in the market for a new orifice tube, try this link here: has a wide selection of orifice tubes on sale. Their options are made to fit some of the most popular cars, come in a range of colors, and are all very reasonably priced.

You can also have a look at the rest of their website for o-rings and other essential parts you may need if you’re attempting to change the orifice tube in your car. 

3. Constantly changing air temperature

This is a tricky one. If you notice the temperature coming from the vents seems to be constantly changing from hot to cool, there are a few different issues that may be occurring.

Warm air can always be caused by issues with the expansion valve, so this symptom might also be a sign of a problem with that part of the system. A blown fuse could also be the culprit in this situation. If the fuse has gone on the air conditioning, certain parts will stop working correctly, and the consistency of the temperature of the air will be affected.

A broken or corroded seal resulting in a small refrigerant leak could also be the issue. If you’re slowly losing refrigerant from the system, it will be challenging to maintain a steady flow of cold air, and you might get alternating temperatures.

Detecting the exact location of the leak will be difficult. Because refrigerant is designed to change to gas at low pressures, once it escapes the system, it will simply evaporate.

Therefore, it’s impossible to see any physical evidence of a refrigerant leak. Instead, you`ll have to use some specially designed tools. One option is to use a black UV light.

Lots of refrigerants have black light enabled dyes in them to make detection easier for this reason. Another device, called a sniffer, can detect signs of the chemicals in the refrigerant and will alert you to areas where its presence is strong.

4. A strong, smelly odor coming from the vents

If you start to notice a strange smell coming from the system, it’s likely that one or more parts will need a good clean. There’s an air cabin filter designed to keep dust and dirt at bay. If your car is old, this may need changing. It’s also possible that the evaporator case is getting old and dirty, resulting in a strong smell.


Understanding the four main parts of the air conditioning system, and what they do to the refrigerant as it passes through, will be hugely beneficial as you try to identify what has gone wrong.

We hope that our troubleshooting tips have helped you to narrow down which part of your car’s air conditioner has broken down and why. Try to take stock of the specific symptoms your air conditioning unit is exhibiting, so you can decipher which part isn’t doing its job.

If you get completely stuck, or if you find the problem but wouldn’t know where to start in fixing it, never feel bad going to a professional! With their experience and skill, they will ensure that no other issues are created accidentally when they take apart the system and put it back together again.

Whether you’re tackling the fixing yourself or not, we hope your car will be a pleasant, cool haven for you again soon.