It's hard to believe air conditioning was once a luxury. Today we take it for granted—until it stops working. But how much do you know about how your AC system actually works? Here's an overview.
The components
There are three main parts to your car's air conditioning—the compressor, the condenser, and the evaporator—as well as a distribution system.
The compressor is responsible for pumping refrigerant through two heat exchangers. Looking like a large metal cylinder, the compressor is located under the hood, where it's driven by a belt from the engine. A hose takes the gaseous refrigerant from the compressor to the condenser, mounted at the front of the car, where it is cooled back into a liquid. After having excess water removed by dessicants, the refrigerant is transported to the evaporator. Here, the temperature is slightly raised so that the liquid refrigerant returns to a gaseous form, which can be distributed throughout the passenger cabin.
The distribution system consists of a fan that moves the air over the evaporator and into ducts. Flaps over the ducts determine whether the air goes to your face or feet. Originally, these flaps were controlled by the driver sliding a lever, but today it's done with electric motors. In simpler systems these are worked by switches, but some vehicles now have automatic AC systems where a computer opens and closes ducts to keep the cabin at the desired temperature.
The science
Refrigerant flows through the condenser, and because it's warmer than the outside air, it cools down. In fact, it cools so much that it condenses back into a liquid. Then, this liquid is transported to the evaporator. This is where the compressor works its magic. Pumping the evaporated refrigerant into a smaller space increases its pressure and makes it hotter.
If you've ever worn a wet shirt on a hot day, you'll know that as water evaporates it takes heat away. The same thing happens in the AC evaporator. Liquid refrigerant is evaporated by the heat of the air blowing across the outside. The air gets cooler and the refrigerant gets warmer. When the refrigerant is returned to a gaseous form, it can be distributed throughout the cabin.
Common problems
There are three things that can go wrong:
- There’s no air, or air coming out of the wrong places.
This occurs when the fan isn't running or the motors controlling the flaps over the air ducts aren't doing their job. - The air doesn't get cold.
Most likely there's not enough refrigerant in the system – it leaks out very slowly over time – although it could indicate a problem with the compressor or the expansion valve. - Air blows cold at first, then warm.
This is not so unusual. It's caused by ice forming in the system, which happens when air and moisture get in.
AC repair
AC systems are very complex and not recommended for the amateur to work on. The best thing to do is to take the car to a reputable service center like that at 3Birds Template, describe the symptoms, and have them take a look.
