Auxiliary Fan

[1][2]AUXILIARY FAN







The [1][2]auxiliary fan is a three stage operation as introduced on the 1996 E38.

Stage 1: Activated simultaneously with the compressor with an ambient air temperature > 10°C (50°F). If the coolant temperature rises to > 91°C the tan will also be switched on. Fan Speed = 1250 RPM.

Stage 2: Activated when the medium pressure switch on the receiver/dryer closes at 17.5 bar. Fan Speed = 2000 RPM.

Stage 3: Activated when the coolant temperature reaches 104°C at the double temperature switch. The stage 3 switched voltage circuit is protected by a 50 amp remote fuse (red). The fuse is located in the electrical carrier forward of the glove box.

[1][2]AUXILIARY FAN CONTROL ('99 MODEL YEAR - E39)







The [1][2]Auxiliary Fan motor incorporates and output final stage that activates the tan motor at variable speeds.

The [1][2]auxiliary fan is controlled by ECM. The motor output stage receives power and ground and activates the motor based on a PWM signal (10-100 Hz) received from the ME 7.2.

The fan is activated based on the following factors:

- Radiator outlet temperature sensor input exceeds a preset temperature.
- IHKA signalling via the K and CAN bus based on calculated refrigerant pressures.
- Vehicle speed
- Battery voltage level







When the over temperature light in the instrument dust is on (120°C) the fan is run in the overrun function. This signal is provided to the ECM via the CAN bus. When this occurs the fan is run at a frequency of 10 Hz.