GF83.40-P-2180-01Q Automatic Air Conditioning Control and Operating Unit, Task

GF83.40-P-2180-01Q Automatic Air Conditioning Control And Operating Unit, Task
- 209.3 up to 31.5.04
- except CODE (581b) Convenience automatic air conditioning

Component Identification:

Task
The AAC control and operating unit (N22) controls and regulates all air conditioning functions for the vehicle interior.

^ harmonizing the preselected and actual temperatures and controlling the air outlet temperature at the air vents.
^ Automatic switchover of fresh air to recirculated air mode.
^ Electrical actuation of refrigerant compressor.
^ Actuation of the electric suction fan engine and AC with integrated control

The following additional functions are also regulated by the AAC [KLA] control and operating unit (N22) and the required information is forwarded to the processing control units via the Controller Area Network Bus Class B (interior) (CAN-B):

^ Heated rear window
^ Stationary heater (on vehicles with code (228) stationary heater)

The AAC control and operating unit (N22) performs the following system actuations:

^ Via the CAN-B:
refrigerant compressor; coolant circulation pump; engine and AC electric suction fan with integrated control
^ Via the A/C bus:
blower regulator; 6 stepper motors for air distribution

The following sensor signal is transmitted by the AAC [KLA] control and operating unit (N22) via the CAN-B:

^ Dew point temperature (the left door control unit and the right door control unit read in this value to implement a demand based heated outside mirror)

The following sensor signals are read in by the AAC pushbutton control unit (N22):

^ Installed sensor: in-car temperature sensor (N22b1)
^ Direct: evaporator temperature sensor
^ Via the CAN-B:
- outside temperature display temperature sensor; refrigerant pressure and temperature sensor
- battery voltage; coolant temperature sensor; engine speed (by the EIS [EZS] control unit)
- vehicle speed (by the instrument cluster)
^ Via the A/C bus:
- air humidity sensor

The AAC [KLA] control and operating unit (N22) reads in the window and door positions as well as the tilting/sliding positions (with code (414a) electric tilting/sliding roof in glass version) to achieve an improved control quality when the roof is open.
The averaged value of the interior temperature with a window open, door open and ground speed = 0 km/h is also recorded for a maximum of 2 min. This ensures that the air conditioning system continues operating immediately with the set interior specified temperature.

The following system settings, which were activated before the engine was switched off, are stored by the AAC control and operating unit (N22) in the electronic ignition switch control unit.

^ AC OFF mode activated (yes/no)
^ Central automatic mode activated (yes/no)

When the engine is restarted, the status stored in the EIS () control unit is reactivated.
The AAC pushbutton control unit (N22) has a diagnostic capability. As a result, any faults which occur are stored in the DTC memory, which can be read out with the help of the STAR DIAGNOSIS system.
When the AAC [KLA] control and operating unit (N22) is replaced, variant coding has to be carried out using STAR DIAGNOSIS.

Blower switch (1)
The blower switch (1) sets the control voltage for the blower regulator in 6 stages via the AAC [KLA] control and operating unit (N22) depending on the setting. This facilitates blower speed control of 0 - 100 %.

Temperature selector wheel on left (2) and right (3)
Turning the left temperature selector wheel (2) or the right one (3) on the AAC control and operating unit (N22) sets the desired interior temperature for left and right separately.

The AAC [KLA] control and operating unit (N22) compares the desired temperature to the temperature in the vehicle interior, which is measured by the in-car temperature sensor (N22b1) in the AAC [KLA] control and operating unit (N22)
Using the comparison between actual values and set points, the AAC control and operating unit (N22) determines the correct position of the left and right blending air flap actuator motors and actuates these separately for left and right. The selected temperature is reached and maintained as quickly as possible, if warming or cooling of the interior is necessary.

Air distribution switch (4)
The air distribution can be set manually or automatically:
^ Manually by turning the air distribution switch (4).
^ Automatically by pressing the Auto button (7).

Turning the air distribution switch (4) on the AAC [KLA] control and operating unit (N22) actuates the various actuator motors for air distribution via the A/C bus.

Apart from the 4 basic settings, a further 8 intermediate settings can be selected.

Defroster button (5)
Pressing the defroster button (5) initiates the defrost function.

The defrost function works according to the following logic:
^ The heating power is controlled by the outside temperature.
^ The entire air flow is directed onto the windshield and front side windows, defroster nozzles open.
^ The air blown in is dehumidified depending on the humidity.
^ The blending air flap actuator motors at left and right regulated.
^ Footwell nozzles closed.
^ Blower capacity 80 %, manually adjustable.

Recirculated air switch (N22s2)
A short press (< 1.5 s) of the recirculated air button (N22s2) actuates the fresh and recirculated air flap actuator motor, which in turn actuates the fresh and recirculated air flap and thus closes the fresh air opening and opens the recirculation duct in order to enable the air to be supplied from the passenger compartment. The LED in the recirculated air switch (N22s2) lights up in recirculated air mode.

Recirculation air convenience closing function
If the recirculated air button (N22s2) is pressed for longer than 1.5 seconds, all the open windows and the tilting/sliding roof are closed automatically (windows and tilting/sliding roof must be normalized) in addition to activating the recirculated air function. The LED in the recirculated air switch (N22s2) lights up in recirculated air mode. Tilting/sliding roof and power windows are operated one after the other in order to avoid current peaks. If the button is pressed again (> 1.5 s), the windows and the tilting/sliding roof return to the previously stored position and the fresh and recirculated air flap goes to the fresh air position (LED off).

The convenience closing function can only be started if the LED in the recirculated air switch (N22s2) is not illuminated. Any window which has been opened manually during this recirculation air phase, remains in this position when the recirculation air function is canceled, all other windows move into the stored position. The positions of the tilting/sliding roof and of the side windows which existed prior to the commencement of the closing operation, are stored by the overhead control panel control unit, the left door control unit and the right door control unit. The windows and the tilting/sliding roof, which were closed by means of the convenience closing function, remain closed if the recirculated air switch (N22s2) is pressed only briefly (< 1.5 s). In this case only the fresh air/recirculated air flap is moved into the fresh air position. The stored positions are canceled when the ignition is switched off.

Auto button (7)
Automatic mode can be activated for the left and right sides simultaneously by pressing the Auto button (7).
In automatic mode, in addition to temperature control the blower output and air distribution are controlled automatically.
The blower speed is continuously controlled depending on the temperature difference between the specified and actual values. The humidity measured with the humidity sensor is used for the electronic control of the air conditioning system in addition to the interior temperature measured with the in-car temperature sensor (N22b1).

AC OFF button (8)
When the AC OFF button (8) on the AAC control and operating unit (N22) is pressed, the LED comes on, the refrigerant compressor is shut off and thus the cooling mode is switched off. The air is no longer cooled and dried.
In vehicles with diesel engines the heater booster control unit is also shut off.
All other functions are retained.
In order to shut off the refrigerant compressor, the AAC [KLA] control and operating module (N22) transmits the shut-off request and the specified value = 0% to the front SAM control unit with fuse and relay module via the CAN-B. At the same time, the refrigerant compressor torque is set to "0" and transferred to the engine electronics and the electronic transmission control via the EIS control unit. The front SAM control unit with fuse and relay module sends the canceled load increase signal to the engine electronics via the EIS control unit and switches the refrigerant compressor off after a defined time delay.

Rest button (with code (670a) residual engine heat utilization system MRA)
The residual engine heat utilization system is switched on by pressing the rest button, which is combined with the AC OFF button (8).
When the engine is switched off, the residual heat heats the vehicle depending on the temperature adjustment on the AAC control and operating unit (N22) and the ambient temperature in the vehicle interior.

The vehicle can be heated for approx. 30 minutes, with the engine switched off. The function is only available, if the ignition is switched off or if the transmitter key in the EIS [EZS] control unit is in position 1. If there is low voltage, the residual engine heat utilization function is automatically switched off.
The flaps for the air distribution and the air volume are regulated automatically.

The residual engine heat utilization function is switched off,
^ if the transmitter key in the EIS [EZS] control unit is moved to position 2,
^ after approx. 30 minutes or
^ if the battery voltage drops below 11 V.