For most car owners, the AC system is a complete mystery. You press the button and are met with a refreshing gust of icy air.
But what happens behind the scenes is actually quite intricate and exceptionally captivating.
So, how does an automotive cooling system function?
An AC system operates by cycling refrigerant, transforming it from a gas into a liquid and then back again. By the end of this cycle, it’s in a cold gaseous state inside the evaporator, at which point external air is blown over it, cooled, and then sent to the cozy cabin.
Ready to take a closer look?
In this guide, we will examine each of the five primary components of your AC system and how they use refrigerants to cool the external air before it reaches the cabin.
Let’s get going!
A Quick Note About Freon And R-12
Freon (also known as R-12) was the primary refrigerant used in most car AC systems until the mid-90s. However, due to its damaging environmental impact, the EPA (Environmental Protection Agency) has banned the import and production of Freon.
Since the mid-90s, automotive manufacturers have used Refrigerant-134a (R-134a), which is less damaging on the ozone and is approved for use in car AC systems. And in 2015, they started using Refrigerant-1234yf (R-1234yf), which is even more advantageous on the ozone.
Table of ContentsShow
Your AC System Explained – The Cycle Of Refrigerant
The High-Pressure Side
Step 1: Compressor
An AC compressor runs off a pulley attached via a belt to your engine’s crankshaft. This powers 5-10 pistons (depending on the design). They draw in low-pressure, cool gas and compress it into high-pressure, hot gas.
The AC compressor is controlled by the clutch, determining if it gets power from the crankshaft. Afterward, this gas goes to the next component of the car’s AC system, which is the condenser.
Step 2: Condenser
When the refrigerant gets to the condenser, it is heated because of the pressure. Its purpose is to collect this heat and move it out of the AC system. You can imagine this as a tiny radiator, where the gas releases the heat as it goes through.
Air is also flowing around the condenser, which cools the refrigerant as it passes through. This causes it to condense, which turns it back into a high-pressure liquid with a reduced temperature. The following step in the cycle is the receiver/dryer.
Step 3: Receiver/Dryer
The receiver/dryer has an entry point and an outlet point. The entry point takes incoming elevated-pressure liquid from the condenser and sends it through a series of filters and desiccants.
If you didn’t know, a desiccant is a substance that absorbs moisture. This is the same material found in items such as shoes and medications to keep them crisp and arid.
The filters remove debris that might cause the system harm, like dust, dirt, and metal particles, and the desiccants eliminate moisture.
What’s the impetus for eliminating excessive moisture?
Because when the refrigerant reaches the expansion valve, it’s cold enough that it might freeze. This can clog the expansion valve and result in an AC system that doesn’t function properly.
The refrigerant is then sent to the expansion valve via the exit point. This concludes the high-pressure side of the AC system.
Next is the low-pressure portion.
The Low-Pressure Side
Step 4: Expansion Valve/Orifice Tube
An expansion valve is essentially a controller for how much refrigerant is allowed to continue on through the AC system. You can think of it as similar to the nozzle on the end of a hose, high-pressure water is introduced, and it expands into a spray as it passes through.
This process not only reduces pressure but rapidly cools the refrigerant as well.
On an AC system featuring an orifice tube, the receiver dryer is replaced with an accumulator. It functions similarly to a receiver dryer but sits between the evaporator and the compressor alternatively.
The difference between an orifice tube and an expansion valve is that the former has a fixed opening. And the latter can adjust its aperture depending on the temperature in the evaporator.
By this point, the refrigerant is now in a low-pressure, frigid state, nearly ready to cool your passenger cabin. But first, it has to pass through the evaporator.
Step 5: Evaporator
The evaporator operates much like a radiator or a condenser, containing tubes that the refrigerant flows through.
As this happens, rather than dispersing heat, it absorbs it, lowering the temperature to about 32 degrees Fahrenheit.
Oddly enough, unlike water, which freezes at 32 degrees, the refrigerant boils. This transforms it back into a gaseous state, enabling it to absorb even more heat. This vapor then flows back into the AC compressor to begin the cycle over again.
How does chilly air enter the cabin when the AC is on? While the refrigerant is sitting in the evaporator, a fan is blowing outside air over it. This causes it to cool due to the low temperature inside. This air then enters your cabin as a cold, refreshing, air-conditioned breeze.
How Does A Car AC System Work?
Well, previously, you might have thought it was captivating.
Thankfully, if you have made it this far in the guide, you should have a considerably enhanced idea of how the air conditioning system in your car operates.
