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E46 Climate Control
Principle of operation
Blower adjustment
The blower rotary dial potentiometer has four settings. Each progressive step represents a
25% increase in blower volume. The control unit determines the desired blower setting by
the signal from the potentiometer and then sends a voltage signal to the final stage unit.
The voltage signal to the final stage unit ranges from 1.8V to a maximum of 7.1V (Normal
blower power in Key Memory).
The final stage unit then regulates blower motor voltage to control the blower volume.
There is no automatic influence on the blower setting.
The blower control potentiometer is the master on/off switch for the IHKR system. The
water valve is closed (energized) in the blower zero (off) position. The LEDs for re-circulat-
ed air and air conditioning are switched off and the compressor is switched off. The rear
defroster operation is not affected by the system being switched off.
Air distribution
The selection of air distribution is carried out using the rotary dial potentiometer (42 steps).
Each step of the potentiometer represents a percentage. The percentage indicates the
desired air distribution setting.
Movement of the stratification flap for face ven-
tilation is carried out by rotating a thumb wheel
between the face vent discharge nozzles. The
thumb wheel is connected to a bowden cable
that moves the flap.
The air distribution for defrost, ventilation and
footwell is performed by a single air distribution
stepper motor that is connected to the M-bus
and controlled by the IHKR control unit.
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