Auxiliary Fan Control

[1][2]AUXILIARY FAN CONTROL







Using a 99 MY vehicle (E38/39/46) for this test, the variable [1][2]auxiliary fan is controlled by the ECM. The auxiliary fan request comes from the IHKA control module via the K-Bus. The fan speed request is based on the refrigerant pressure sensor input to the IHKA. Additional factors monitored by the ECM that influence fan operation are:

- Radiator outlet temperature sensor (exceeds the preset temperature)
- Vehicle speed
- Battery voltage level

The [1][2]auxiliary fan motor incorporates an output final stage that activates the fan motor at variable speeds. The output stage receives an output signal (pulse width modulated 10-100 Hz) from the ECM which activates the motor.