Control Panel/Module

IHKA E38 CONTROL PANEL/MODULE (up to 5/96 production)







Functionally, the most significant difference between the IHKA E38 control panel and earlier IHKA control panels is that, on E38 vehicles, the control panel is combined with the control module. Despite this tact, the IHKA E38 control panel/module is about the same size as earlier control panels, and it has only three connectors.

The control panel/module face is also quite different from previous IHKA control panels. Features are described below, from left to right:

Air Distribution Buttons: There are four left (and three right) air distribution buttons. The driver can let the control module determine air distribution (automatic mode), or select up to three specific discharge locations (windshield, face vents, and/or footwells). The front passenger can also select automatic mode, or choose footwells and/or face vents.







If the "up arrow" button is pressed, air flows from the windshield defroster outlets all along the base of the windshield. The face vent, footwell and console outlets are closed, and the mixing flaps move to the "warmest air" position.







If the "left arrow" (or "right arrow") button is pressed, air flows from the face-vent outlets on the left (or right) side of the instrument panel and the footwell outlets on that side of the interior close.

Only the "left arrow" button affects defroster and console flap operation. If the "left arrow" button is pressed, the defroster and footwell outlets are closed. The console flap opens so long as the rear outlet thumbwheel indicates "open."







If the left (or right) "down arrow" button is pressed, air flows from the footwell outlets under the the left (or right) side of the instrument panel and the rear seat outlets on that side, too. The mixing flap for the left (or right) side of the interior moves to the "warmest air" position.

Only the left "down arrow" button affects defroster and console flap operation. If the left "down arrow" button is pressed, the defroster flaps are closed. The console flap opens so long as the rear outlet thumbwheel indicates "open."







While there is an "AUTO" button for each side of the interior, the right button does not influence air intake location (fresh/recirc.), defroster flap operation, or console flap operation.

The basic function of the left and right "AUTO" buttons is, however, the same. When "AUTO" is pressed, the control panel/module selects the air distribution points based on the desired temperature, interior temperature, ambient temperature, (all "Y-factor" inputs) and blower speed.

When cooling is required, the face vent flaps are opened and the footwell flaps are closed; when heating is required, the footwell flaps are opened and the face vent flaps are closed.







Left and Right Desired Temperature Displays: When the IHKA system is turned "On," the left and right LED displays show the desired temperatures. LED brightness varies according to ambient light conditions.







Left and Right Desired Temperature Rocker Switches: Desired temperatures are selected using rocker switches. Pressing the blue "down" arrow decreases the desired temperature by 1°F (or 1/2°C) each time the button is pushed. Pressing the red "up" arrow increases the desired temperature. Large changes can be made by pressing and holding the "down" or "up" arrow.







Left and Right Blower Thumbwheels: There are separate blower control thumbwheels for the left and right sides. The control panel/module uses inputs from both to determine blower speed and face vent flap position.

The left blower thumbwheel is referred to as the master controller since:

- it has priority over other inputs when it is in the "0" and maximum-speed positions
- it is also used to turn the IHKA E38 system "Off" and "On"







Interior Temperature Sensor: Interior air is sampled using a temperature sensor located inside the control panel. Air reaches the sensor through an opening in the control panel face. Like other IHKA systems, IHKA E38 also uses a small electric fan to pull air over the temperature sensor.







Panel Illumination Photocell: A small photocell, located to the left of the interior temperature sensor, monitors ambient light levels. The control panel/module adjusts the brightness of the desired temperature displays using this input.







Maximum Defrosting Button: The maximum defrosting button has priority over all other IHKA system functions. When the button is pressed:

- the fresh air flaps open fully and
- the recirculating air flaps close fully and
- the mixing flaps move to the "warmest air" positions and
- the defroster flaps open fully and
- all other air distribution flaps close fully and
- the blower motor runs at maximum speed

If engine coolant temperature (supplied over the K-Bus) is above 32°F (0°C):

- the auxiliary coolant pump is activated

Neither the rear window defroster nor the A/C compressor turn on automatically, but will operate if the appropriate button is pressed.







AUC/Recirculating Air Button: The recirculating air/AUC button controls air intake location. During normal operation, fresh air is drawn into the climate control system and heated or cooled.

Pressing the recirculating air/AUC button once activates the automatic recirculating air function and lights the left LED. An AUC sensor, located in the engine compartment, monitors the level of oxidizable gases in ambient air and notifies the control panel/module when these gases reach a specified level. When this occurs, the control panel/module automatically:

- closes the fresh air flaps and
- opens the recirculating air flaps







Refer to "IHKA E38 Special Functions" later in this Handout for more information on the AUC feature.
Pressing the recirculating air/AUC button twice causes the control module to light the right LED and immediately:

- close the fresh air flaps and
- open the recirculating air flaps







Rear Window Defroster Button: Pressing the rear window defroster button activates rear window heating at full power for either 17 or 10 minutes, depending on ambient temperature. The defroster is then shut off. Pressing the button again runs the defroster for another 5 minutes.







A/C Compressor Button: Pressing the "snowflake" button turns on the A/C compressor. The control panel/module activates the compressor directly, and interfaces with the engine control module for idle stabilization and [1][2]auxiliary fan operation.







"Rest" Button: The "Rest" button is used to activate the rest heating function. This function provides passenger compartment heating after the ignition is switched "Off".

Refer to "IHKA E38 Special Functions" later in this Handout for more information on the Rest function.

Viewed from the bottom, the IHKA E38 control panel/module has the following features:







Since the beginning of production, setting the temperature selector on the driver side of the IHKA to its minimum or maximum values would result in overriding the temperature setting on the passenger side. Both sides would either have heater off and maximum cooling with air conditioner on (mm. value) or full heat (max. value), regardless of the setting selected on the passenger side.

As of production date 9/95, the override function of the passenger side temperature settings will no longer be performed (IHKA control units with part numbers #64118369781 or #64118372482). Each side will work exactly according to its temperature setting, regardless of the temperature the other side has chosen.

Since the original IHKA control unit of vehicles produced before 9/95 is no longer available spare part for the IHKA control unit will also have this function change.

If replacement of an IHKA control unit becomes necessary on a vehicle which originally had the override function, the customer should be informed about this override function change in his car.

Due to changes made to IHKA control panels on 7 series (E38), the older style panels are no longer available. If replacement becomes necessary the new style panel must be retrofitted, and a customer has to be informed about new features of the unit.

CHANGES TO 7 SERIES (E38) IHKA CONTROL PANEL:





The IHKA control panel has changes in appearance and operation. The blower speed control wheels have been replaced by rocker switches. The push buttons for Front and Rear defrost, NO control and AUC control are now mounted in a single row at the bottom center of the control panel

- after 9/96 production

The major changes in the operation of the system as of 9/96 are:





A new "AUTO-symbol" is used in the LCD display in addition to the illuminated LED on the "AUTO-button".

- The "AUTO-symbol" in the LCD indicates the automatic fan speed program being activated.
- The illuminated LED on the "AUTO- button" indicates activation of the automatic air distribution program.
- When both are displayed, the system is in the fully automatic mode.

If one of the manual distribution buttons is selected, the automatic air distribution is cancelled and the "AUTO-button" LED goes out.





If one of the manual distribution buttons is selected, the automatic air distribution is canceled and the "AUTO-button" LED goes out (e.g. on the illustration - passenger face vent button was selected).

However, the fan speed remains in the auto mode, with "AUTO- symbol" being displayed on the LCD.

If the fan rocker switch is pressed, when the system is in the AUTO mode, the blower speed is switched to manual control. The "AUTO-symbol" in the LCD display goes out.

However, the air distribution remains in the automatic mode with the LED being illuminated on the "AUTO-button".