Blower Motor
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.
A dual squirrel-cage blower is used (on most BMWs) to propel air across the evaporator and/or the heater core and through the plenum to the vents. On BMW A/C systems, the blower speed is controlled by resistors/transistors that vary the amount of voltage applied to the blower, depending on the air volume control knob setting. In IHKA systems, the blower speed is controlled electronically.
Whenever the A/C is switched on, the fan runs at speed "1" or higher. Without the fan working, the evaporator could ice up, as humid air comes in contact with the fins.