Climate Control: Refrigerant

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 uses refrigerant to absorb heat from the air that passes through the evaporator. Refrigerants are special materials that are vapors at room temperature and liquids at much lower temperatures. Automotive refrigerants, for example, boil at -16°F to -22°F (-27°C to -30°C). Refrigerants are also able to contain and transport a large amount of heat, efficiently; and they can be evaporated and condensed over and over without being damaged.

In the air conditioning system, liquid refrigerant under high pressure flows through a small hole into the evaporator, where the pressure is then greatly reduced. When the pressure drops, the refrigerant boils and changes from a liquid to a vapor. As it changes its state, it absorbs a large amount of heat.

As the air passing through the evaporator gives up some of its heat, it becomes colder; it can then be blown into the passenger compartment, to cool it.

Once the refrigerant has absorbed heat from the air, it is returned to the compressor. The A/C system removes the excess heat from the refrigerant as the refrigerant passes through the condenser.

There are two types of refrigerant used in BMW vehicles; these will be discussed later in