Heat Transfer
WARNING: This page does not describe the selected car, but rather 41 other vehicles, including the 2003 BMW M5, 2003 BMW M3, 2003 BMW 540i, 2003 BMW 530i, and 2003 BMW 525i. However, it is still accessible from the selected car via links, so may be relevant.
An air conditioning system's efficiency is based on how well it moves heat. Heat always travels from warm to cold. The reverse is never true. For example, if a hot cup of coffee is left standing, it will cool off, while a cold soda will get warm. The heat from the warm coffee moves to the cooler surrounding air. The heat from the surrounding air moves to the cooler soda, until a balance is reached.