In the winter, for example, you may turn the key and immediately start blowing into your freezing cold hands as you wait for your heating system to warm up, intermittently grabbing quick sips of steaming hot coffee while cursing the fact that you’ve barely seen the sun for the better part of a month and you’re sick and tired of it and you should have just moved to Florida when you had the chance because 99 degrees in June, July and August cannot be worse than the ceaseless winter that’s turned your cul-de-sac into a frozen wasteland.
In the summer, on the other hand, you may turn the key and immediately roll down your windows before pushing your face toward the car air conditioner vents as chilled, humidity-free air starts pouring into the cabin. A satisfied sigh may even slip from your lips as you temporarily escape an atmosphere so full of humidity you swear you could wear it.
In the latter scenario, it’s unlikely you’ve ever stopped to think about what’s going on mechanically to get a gloriously cool breeze flowing over your cheeks, but it’s actually a pretty nifty happening.
How does car air conditioning work?
Here’s exactly what happens when you flick the switch to turn your car air conditioner on:
- Initiating your AC system activates a compressor inside your vehicle’s engine compartment, which, as implied by its name, compresses and pressurizes a refrigerant. We’ll touch on refrigerants again in a bit.
- The compressed refrigerant moves to a condenser at the front of your vehicle between your grille and radiator. A fan cools the refrigerant down and it leaves the condenser as a liquid.
- After a short visit to a receiver/dryer, which removes moisture from the AC system, the liquid refrigerant passes through an expansion valve or orifice tube, depending on the make and model.
- Passing through the valve or tube turns the refrigerant back into a gas, which significantly reduces its pressure and drops its temperature.
- An evaporator inside the passenger compartment just behind your dashboard removes leftover heat as a blower sends air over the cooled refrigerant into your vehicle. It’s a similar effect to blowing across an ice cube.
- The refrigerant returns to the compressor and the process starts over.
What is a refrigerant?
A refrigerant, by definition, is something that refrigerates; cooling or freezing something. A refrigerant called R12 was the most common type used in air conditioning for cars for decades. It was banned by the Environmental Protection Agency about 20 years ago, however, because of concerns over potential harm to the ozone layer. Its replacement, R134A, is now facing a similar fate. The EPA is calling for it to be phased out in vehicles over the next several years in favor of more environmentally friendly substances.
What does it mean to have the AC system charged?
In theory, you should never have to charge your AC system. In reality, many drivers have their systems charged because there is a leak somewhere in the system such as a seal, line or even major component such as the compressor, condenser or evaporator. Some technicians will run colored dye through the system to identify potential trouble spots.
What about the stuff at the local automotive parts store for a DIY charge?
AC charge kits are pretty common but should you decide to tackle such a project it’s important to be careful you don’t overcharge the system by adding too much refrigerant. Doing so can have the same impact as not having enough of the chemical. Be sure to follow the directions that come with each kit.
What’s the difference between the fresh air and recirculation cycles?
A vehicle’s recirculation cycle uses already refrigerated air from the cabin and runs it through the air conditioning system once more. While this might seem like a way to get even colder air, it’s a good idea to use your fresh air cycle. Doing so can limit the potential for mold build-up in the system.
To learn more about car parts and how they work, visit AAA.com/Car101.
Written with contribution from AAA’s Car Doctor, John Paul.