Structure and inner electrical connection

The drive of the electric fan is a brushless motor. The electric fan has its own electronic evaluation unit and its speed is regulated by a pulse-width modulated signal. The pulse duty factor in the normal operating mode (100 Hz) is converted into a speed signal.

• 7% pulse duty factor: Standby mode (electronic evaluation unit is kept awake)
• 11% pulse duty factor: minimum fan speed (33 % of rated speed)
• 93% pulse duty factor: maximum fan speed
• 97% pulse duty factor: command for self-diagnosis of the electronic evaluation unit
  Fig 1: Electric Fan - Wiring Diagram

  Courtesy of BMW OF NORTH AMERICA, INC.