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Driving in the summer can be a completely different experience if your car doesn’t have an AC unit. If all you can do is crack open a window or sunroof, you’ll never be as comfortable on a hot day than if you can switch on your air conditioning.
Anyone who has a car with an AC unit can attest to this. Within seconds, your car can go from a humid, sweltering environment that no one could stand a few minutes inside, to a cool, calm place that makes a long drive a breeze, no matter how hot it is outside.
This form of technology was invented back in 1940, but it’s only recently that you’ll find it inside the vast majority of cars, with experts dating 2010 as the year that it became an industry standard.
Many people know what AC feels like, and have experienced its results, but much fewer people know exactly how it works. If you’re one of these people, then you’ve come to the right place, as we’re now going to find out exactly what AC does and how it works. Let’s go.
What is the Purpose of Air Conditioning in a Car?
An air-conditioning unit inside a car does a few different jobs. The first is that it sends cool air into the car’s passenger area. As it does this, it removes moisture from the air. This is why people often feel that an air-conditioned car reminds them of a crisp winter’s day. Of course, when you’re driving through conditions where it’s humid and hot, air conditioning is a must, as it provides you with incomparable comfort.
The AC will often be used in winter. It can be used for the opposite purpose than in summer, as the air can also be heated. This can then be used to defrost the car.
How Does a Car’s AC Unit Work?
Before we can explain how the AC unit works, we need to know what components comprise the system, as each part plays an essential role in producing cool, crisp air.
The key components in an AC unit are:
- The Compressor
- The Condenser
- The Receiver-Drier
- The AC In-Line Filter
- The Expansion Valve or The Orifice Tube (Depending on the system)
- The Evaporator
- The Accumulator
As you will have seen, there are two options for one of the components, and that’s because there are two main air-conditioning systems found in most automobiles. We’ll look at the process with both of them, but they work in much the same way. The only big difference is that one system features an expansion valve, and the other system has an orifice tube.
Let’s look at how it works now that we’ve familiarized ourselves with the AC unit’s major components.
Step One: Refrigerant is needed to make the whole system work. Without it, then your system is not able to function. That means that every AC system has to be filled with a refrigerant gas before it can work. Several gases are used for this purpose, but the most common is ‘1, 1, 1, 2-Tetrafluoroethane,’ which is referred to under different names. It’s often colloquially called Freon gas because of the prevalence of Freon manufactured gases, but Freon is simply one company that sells this gas to AC unit manufacturers.
Step Two: Now that the system has been filled with a refrigerant, then it’s ready to work. The first stage in the process is for the gas to be compressed. Of course, this is the job of the compressor. The refrigerant becomes extremely hot when the compressor compresses it. Once it has reached a certain temperature, then it’s sent to the next component.
Step Three: The opposite process now happens in the condenser. The refrigerant is condensed via several coils. This will turn the hot gas into a very cool liquid. Once this liquid has reached the end of the coils that the condenser is composed of, it has been sufficiently cooled and can move onto the next stage. Noted that the pressure produced in the previous step remains, but now we have a cold liquid rather than a hot gas, thanks to the condenser.
Step Four: Now is the time for the receiver-drier. This component has two different purposes. It will get rid of any moisture or water that has found its way into the AC unit. Water can be the death of an AC unit, which is why the receiver-drier is essential. It does this process by drying the air in the system.
Step Five: Just like water, the last thing your AC unit needs is debris or hard granules going through the system, which is why there is an AC inline filter. This makes sure that the debris will not travel onto step six, which is where we’re going now.
Step Six: This is where the two different systems briefly deviate from each other. In an expansion valve system, the liquid refrigerant will now be transformed into a mist or spray. If your system features an orifice tube, then the refrigerant won’t turn into a mist. Instead, the pressure will be removed from it, turning it from a high-pressure liquid into the opposite – namely, a low-pressure liquid.
Step Seven: Now, it’s time for the evaporator to come into its own. Its job is quite simple. The mist or low-pressure liquid is sent through the evaporator. When it comes out the other side, it becomes cool air. You then feel while you’re sat inside your car, thanks to a blower motor. This is not the end of the journey, though, as the refrigerant still needs to be cycled back around the car’s AC system. This refrigerant is taken to the accumulator. And this process then helps to remove moisture from the air.
Does the Refrigerant in a Car’s AC Unit Need to be Replaced?
Yes. There are times when your car will require a top-up of refrigerant. It’s like the oil in your car. Sometimes you can top it up, but other times, you might need a whole change of refrigerant. This process is often referred to as an AC recharge. You can get this job done by a professional mechanic for an affordable fee.
If you’re not familiar with the internals of a car – or don’t feel confident topping up the refrigerant in your car yourself – then it’s best to consult a professional anyway. They can look at the system and see if a simple top-up is best for you, or if a recharge would be a better option.
Summary
An AC unit is a highly effective system that relies upon key components and a refrigerant gas – to turn a stuffy, hot car, into a crisp, cool one. In seven main steps, the cycle is complete.
