Air Distribution

IHKA E32 AIR DISTRIBUTION







IHKA E32 air distribution outlet locations are shown above. On IHKA E32 systems, stepper motors are used to control all air distribution flaps.

Also, separate air distribution push buttons on the IHKA control panel allow the driver and front seat passenger to select different air discharge locations.

And, on IHKA E32 systems, air flow from the console rear outlet is controlled using a stepper motor and flap located on the IHKA housing assembly.

Defroster Outlets
Air flow from the windshield defroster outlets (and the left and right door glass defroster outlets) is controlled by defroster flaps, which are operated by the control module. The defroster flaps, while "split" left/right; they are operated as a pair using input signals from the left air distribution push buttons (and programmed control module information).

In general, the defroster flaps:
- are half open when the left "up/down" or "down" mode is selected and the A/C compressor Is turned off (regardless of Y-factor)
- close while the system is cooling and during light heating demand (Y-factor from -25% to +20) while the A/C compressor is operating
- are half open when heating demand increases (left Y-factor is 35% and above)
- are about 1/3 open when the left "AUTO" mode button is pressed, the Y-factor is between -25% and +50%, and the A/C compressor is off
- open progressively as heating demand increases (they are half open at a left Y-Factor of 100%) and the A/C compressor is off
- are completely closed when "AUTO" mode is selected, the Y-factor is between -25% and +20%, and the A/C compressor is operating
- fully open when the maximum defrosting button is pressed (all other distribution flaps are fully closed)

Face Vent Outlets
Air flow from the top, center, left and right face vents is controlled by the left and right face vent flaps, which are operated separately by the control module.

Face vent flap operation strategy does not depend on whether the A/C compressor is on or off:
- When the "up/down" button on one side is pressed, the face vent flaps on that side are fully opened.
- When the "down" button on one side is pressed, the face vent flaps on that side are fully closed.
- When the "AUTO" button is pressed, the face-level flaps are fully open during heavy cooling demand (Y-factors from -25% to +15%) and fully closed during heavy heating demand (Y-factors between 90% and 100%). For Y-factors between 15% and 90% the face vent flaps close with increasing Y-factor.

A few minutes after engine shutdown, both face vent flaps close. At engine restart, the flaps move to the appropriate position, according to the control module inputs.

Footwell Outlets
Air flow from the left footwell outlet and the left rear (underseat) outlet is controlled by the left footwell flaps. The right footwell flaps control the airflow from the right side outlets.

When "down" or "AUTO" mode is selected, footwell flap operation is not affected by whether the A/C compressor is on or off:
- Pressing the "down" button on one side causes the footwell flaps on that side open fully, regardless of Y-factor.
- Pressing the "AUTO" button causes the footwell flaps to fully close during system cooling and light heating (Y-Factors between -25% and +30%) and fully open during heavy heating demands (Y-factors above 43%).
- when the "AUTO" button is pressed and the Y-factor is between 30% and 43%, the footwell flaps open linearly (from fully closed to fully open) with increasing Y-factor.

When "up/down" mode is selected, footwell flap operation does depend on whether the A/C compressor is on or off.
- When the "up/down" button on one side is pressed and the A/C compressor 16 off, the footwell flaps on that side open fully regardless of Y-factor.
- When the "up/down" button is pressed and the A/C compressor 16 operating, the footwell flaps are half open during system cooling and light heating (Y-factors between -25% and +20%) and fully open during heavier heating demands (Y-factors above 30%).
- Between Y-factors of 20% and 30%, the footwell flaps open linearly (from half open to fully open) with increasing Y-factor.

Console Rear Outlet
Air flow from the console rear outlet is controlled by the console outlet flap. The control module operates the flap using input from the left air distribution push buttons, the console outlet switch (a micro switch included in the thumbwheel assembly), and the left Y-factor.

Console flap operation does not depend on whether the A/C compressor is switched on or off:
- When the left "up/down" button is pressed, rotating the thumbwheel to the left of the rear outlet upward (switch closes) causes the console rear outlet flap to fully open, regardless of Y-factor. Rotating the thumbwheel ail the way down (switch opens) causes the flap to fully close.
- When the left "down" button is pressed, the console rear outlet flap is always fully closed, regardless or rear outlet thumbwheel position.
- When the left "AUTO" button is pressed (and the rear outlet thumbwheel is rotated upward), the console rear outlet flap is fully open at Y-factors from -25% to +20%. Above Y-factors of 70% the outlet is fully closed.
- When the left "AUTO" button is pressed (and the rear outlet thumbwheel is rotated upward), the console rear outlet flap closes linearly as Y-factor increases from 20% to 70%. Rotating the thumbwheel all the way down (switch opens) causes the flap to fully close, regardless of Y-factor.

Rear passengers can also rotate the thumbwheel to throttle airflow from the console outlet.


NOTE: Vehicles produced from 6/90 do not have the console rear outlet switch or wiring. On these vehicles, the control panel continuously provides a "rear outlet open" request to the control module, 60 flap position depends entirely upon the mode selected and the left Y-factor.


Shutdown Operation
Three minutes after engine shutdown, the control module opens the defroster flaps fully and closes all the other air distribution flaps. Then, when the engine is started, air flows from the defroster outlets for the first few seconds of system operation (if the IHKA system is turned on), to ensure that the windshield is cleared first. The control module then resumes normal operation, moving all the flaps to their appropriate positions. (The only exception to this sequence occurs if the cold-start arrest function is activated at start-up; the cold start arrest function is described later in this Handout under "Special Functions.")