Air Flow Control Wheel

Operation
The IHKA control unit takes up operation when the ignition is switched on. The IHKA can be switched on and the nominal value for the air flow set with the air flow control wheel. An increase in the set air flow rate by the wind during driving is largely compensated by the fresh air flap closing dependent on the vehicle speed. The blower is switched off via terminal 50 when starting the vehicle.

A switch is coupled with the air flow control wheel to ensure the blower can take up emergency operation in the case of a defect in the air flow control wheel, failure of the control unit or a defect in the output stage electronics. In the maximum position of the air flow control wheel, this switch switches positive to a relay integrated in the output stage, thus bypassing the output stage electronics. The blower then runs at full power. This switch is not included in the diagnostic procedure for the control unit. It is protected in the case of a short-circuit by a resistor (PTC) connected in series to the switch.