The AC system is composed of many parts that functions hand in hand to achieve a single goal, and that goal is to cool the vehicle's interior. The different parts that make up an auto air conditioning system are all important for the system's function. In every system, however, there is always a single component that is considered the most important. This component is often termed as the heart of the system. In the auto air conditioning system, this component is the AC compressor.

The AC compressor is a mechanical pump that is driven by a belt attached to the vehicle's engine. Like the human heart, the AC compressor pumps fluid so that it would flow in a closed loop through the various parts of the system. Instead of blood, however, the AC compressor pumps refrigerant, which is the main element responsible for absorbing all the heat that accumulates inside the vehicle's cabin.