Auxiliary Fan Control

IHKA E32 [1][2]AUXILIARY FAN CONTROL







E32 vehicles are equipped with a two-speed "pusher" type fan, which mounts ahead of the A/C condenser.

The [1][2]auxiliary fan can be triggered three different ways:
- By a request from the IHKA control module (normal-speed operation)
- By high refrigerant pressure (high-speed operation)
- By high engine coolant temperature (normal- or high-speed operation)

Fan activation by the IHKA control module occurs one of three ways, depending upon vehicle model year;
- For 1988 vehicles, pressing the "snowflake" or recirculating air buttons causes the IHKA control module to energize a relay (the A/C Motronic relay) and the relay sends power directly to the [1][2]auxiliary fan motor normal speed winding.
- On 1989 to 1992 vehicles (schematic shown at left), the control module energizes the A/C compressor control relay and the normal speed relay at the same time. So the [1][2]auxiliary fan and the A/C compressor get power simultaneously.
- For 1993 and 1994 vehicles, the normal speed relay is placed in the signal circuit between the IHKA control module and the engine control module. For the relay to be energized, high-side refrigerant pressure must be within limits.

Refrigerant pressure and coolant temperature triggered operation of the [1][2]auxiliary fan are the same for all E32 vehicles, regardless of model year or engine
type:
- When high-side pressure exceeds 260 psi (18 bar), the fan runs at high speed; when pressure drops to about 218 psi (15 bar), the fan shuts off.
- When coolant temperature reaches 196 °F (91 °C), the fan runs at normal speed.
- If coolant temperature reaches 210 °F (99 °C), the fan runs at high speed.