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Nearly every car, truck and SUV on the road today has air conditioning.  Once a cantankerous, unreliable and expensive option on upscale car models, late model cars feature cabin cooling that is an efficient, relatively care free standard feature.  You know how to mash a button or turn a dial and feel the cool breeze start blowing from your vents, but just how does the hot stuff under your hood make ice cold air inside your cabin?

 

The magic starts with a gas called Freon.  When Freon is squeezed into a small space and then allowed to expand an endothermic chemical reaction makes this incredible gas cold.  Freon gets so cold that sometimes on humid days you might find the A/C hoses under your hood wearing a coating of ice, even in the heat of summer. 

 

But compressing Freon in hoses and pipes is not all that needs to happen to make your passenger compartment cool and breezy.  In short, a compressor must squeeze the Freon into a small space, push it through an orifice into a larger tube and then quickly circulate the cold gas through a heat exchanger, which looks like a small radiator hidden under your dash.  A fan blows air over the cold exchanger and out of your vents. 

 

Keep in mind this incredible system is totally dependent on having enough Freon to keep things cold.  Freon can slowly escape from even the most expensive systems.  Freon is expensive and if it gets too low, expensive parts in the system degrade quickly.   Having a qualified service center check your Freon level every six month, and top it off if needed is a great way to maintain your cool. 

 

So now you know how cold air gets produced by the AC system but you may not know how to take full advantage of the systems features.  In fact, you may not know what some of those features even are.

 

First of all, unlike older AC systems that turned the compressor on and off, modern compressors run nearly constantly unless you manually turn them off with the "AC off" button.  This is because air conditioning dries the air out in your car, preventing your window from fogging up even in the winter.  All that fan driven air also pushes the air in your cockpit out of flow through vents, usually hidden under your rear bumper wrap, exchanging the staid air for newer, fresher air up to twice per minute.

 

Now let's talk about the most misunderstood function of your air conditioning system by far and away; the MAX A/C button or setting.  As the name implies, maximum air conditioning makes colder air by recirculating the air it has already cooled over and over.  If the air outside is hotter than the air in the cabin MAX A/C is awesome.  But when you get in your hot car the air inside is much hotter than the air outside.  To get the most of your air conditioning system leave the car in the normal mode, which brings in outside air for cooling, and then switch to MAX A/C once the cabin is cool.  Your interior will get much more comfortable much more quickly this way.

 

Understanding how systems in your car like the temperature control work  is always interesting.  Knowing how to get the most out of them makes that knowledge a useful and enjoyable part of owning a car.