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E46 Climate Control
The stepper motor drives a cam/lever assembly (1) that articulates all three air distribution
flaps. The position of the cam is confirmed by the air distribution micro-switch (2).
The air distribution micro-switch is provided
5V by the IHKR control unit. The micro
switch is closed by the rotating cam lobe in
two positions:
• Full defrost 97% to 0%
• Mixed face vent/footwell 37%
(quick confirmation)
When the switch is closed the signal at the
control unit goes low, informing the control
unit that it has reached that particular
position. The display in diagnosis recog-
nizes this position as “off”.
A reference run is initiated the first time KL30 is switched on to the IHKR control unit. The
reference run is required to determine the position of the cam disc. The cam disc is
rotated until the micro-switch sends a signal to the control unit. After the reference run is
completed, the control unit recognizes what position the cam disc is in and thus the
position of all three air distribution flaps.
If the air distribution micro-switch is not able to produce a signal at the correct position, the
control unit will continue to operate the stepper motor at an estimated position. Eventually
the air distribution setting will not match the actual output. The air distribution micro-switch
circuit is fault monitored.
Temperature control
The desired interior temperature is set with the rotary dial potentiometer (34 steps). The
face of the dial itself has no marked temperatures, just a blue, white and red line that rep-
resents a comfort zone.
All of the air flowing into the IHKR housing must pass through the evaporator first before
being re-heated by the heater core. This is the principle used by all IHKR and IHKA sys-
tems.
The IHKR maintains the temperature of the discharge air by cycling the water valve to reg-
ulate the temperature of the heater core. The duty cycle applied to the water valve is based
on the “Y-factor” (correcting variable) and other variables.
Located on the right side of the IHKR case
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