IHKA E36 Air Intake
The fresh air flaps stepper motor operates only when the ignition switch is in "Run." At engine shut-down, the fresh air flaps stay in their "last-used" position. When the ignition switch is again turned to "Run," the control module/panel operates the stepper motor to move the flaps, if necessary.
When open, the flaps are positioned according to road speed; the flaps close incrementally with every 12.5 mph change in road speed (to prevent the flaps from continually opening and closing due to slight changes in speed). At 85 mph the fresh air flaps are only 20% to 40% open (depending on blower speed).
In the recirculating air mode, the fresh air flaps are 20% open.