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Home >> Mercedes Benz >> 2012 >> SLK 250 (172.477) L4-1.8L Turbo (271.861) >> Repair and Diagnosis >> Heating and Air Conditioning >> Control Assembly >> Description and Operation

Control Assembly: Description and Operation




GF83.40-P-3000RD Component Description For Automatic Air Conditioning Control and Operating Unit
MODEL 172.4





Without code (581) Comfort automatic air conditioning and without code (494) USA version, vehicles for the Economic Commission for Europe (ECE)
N22/7 Automatic air conditioning control and operating unit

Location
*The control and operating unit is located in the center console.

In vehicles outside of the ECE, the "OFF" button is installed instead of the "REST" button. By pressing the "OFF" button, the automatic air conditioning is switched off completely.





Without code (581) Comfort automatic air conditioning with code (494) USA version
N22/7 Automatic air conditioning control and operating unit





With code (581) Comfort automatic air conditioning and without code (494) USA version
N22/7 Automatic air conditioning control and operating unit





With code (581) Comfort automatic air conditioning and without code (494) USA version
N22/7 Automatic air conditioning control and operating unit

Design
The control and operating unit includes, without code (581) Comfort automatic air conditioning, the following operating and display elements:
- Rear window heater button (N22/7s1)
- Air recirculation mode button (N22/7s2)
- Defrosting button (2)
- "MAX COOL" button (3.2) (with code (494) USA version)
- "REST" button (3.3) (in vehicles for ECE)
- "A/C" button (4.2)
- Temperature selector wheel (12)
- Windshield air distribution button (13)
- Center air distribution button (14)
- Lower air distribution button (15)
- Air volume selector wheel (16)
The control and operating unit includes, with code (581) Comfort automatic air conditioning, the following operating and display elements:
- Rear window heater button
- Air recirculation mode button
- "AUTO" button (1)
- Defrosting button (2)
- "ZONE" button (3.1) (without code (494) USA version)
- "MAX COOL" button (3.2) (with code (494) USA version)
- "A/C and REST" button (4.1) (without code (494) USA version)
- "A/C" button (4.2) (with code (494) USA version)
- Right temperature selector wheel (5)
- Air distribution button (6)
- Increase air volume button (7)
- Reduce air volume button (8)
- "OFF" button (9)
- Left temperature selector wheel (10)
- Display (11)

Task
The control and operating unit has the following tasks:
^ Operation of the vehicle's climate control
^ Reading in of sensors and signals
^ Evaluation of input factors
^ Actuating components

Operation of the vehicle's climate control
It is operated with the following controls:
^ Controls that do not depend on the equipment
^ Controls without code (581) Comfort automatic air conditioning
^ Controls with code (581) Comfort automatic air conditioning

Controls that do not depend on the equipment
^ Rear window heater button
^ Air recirculation mode button
^ Defrosting button
^ Temperature selector wheels

Rear window heater button
The rear window heater (R1) is switched on when the rear window heater button is pressed. The light-emitting diode (LED) illuminates during operation.
The operating time of the rear window heater is calculated by the rear SAM control unit with fuse and relay module (N10/2) depending on the outside temperature, interior temperature and vehicle speed.

Air recirculation mode button
By actuating the air recirculation mode button for t < 1.5 s the fresh air/recirculated air flap is closed to prevent air from flowing in from outside. The air only circulates in the vehicle interior and unpleasant odors and harmful gases are kept out.
The LED above the air recirculation mode button lights up during operation.
Pressing the air recirculation mode button for t > 1.5 s activates comfort air recirculation closing.
In the process, the side windows are closed. If the air recirculation mode button is pressed again for t > 1.5 s, the side windows return to their previous position.
Side windows, which were manually opened during the air recirculation phase, do not return to their previous positions once the phase is over.

Defrosting button
Pressing the defrosting button sets the temperature to "maximum" and distributes the air flow to the defroster vents. All the other flaps are closed. The blower output is regulated to match the coolant temperature.
The LED lights up when the function is activated.

Temperature selector wheels
The desired specified temperature can be set by manually turning the corresponding temperature selector wheel. The selected setting is displayed by LEDs around the circumference of the selector wheel.

Controls without code (581) Comfort automatic air conditioning
^ "MAX COOL" button (with code (494) USA version)
^ "REST" button (in vehicles for the Economic Commission for Europe (ECE) without code (494) USA version)
^ "A/C" button
^ Air distribution buttons
^ Air volume selector wheel

"MAX COOL" button (with code (494) USA version)
Pressing the "MAX COOL" button raises the blower output to 100%. The specified temperature values are regulated to "Maximum cold". The LED in button is on.

"REST" button (in vehicles for the Economic Commission for Europe (ECE) without code (494) USA version)
Pressing the "REST" button activates the residual heat utilization function.
This function is only possible with circuit 15 OFF.

"A/C" button
Pressing the "A/C" button when the engine is running switches the A/C compressor (A9) on or off. All other functions are retained.
The LED lights up when the refrigerant compressor is switched on.

Air distribution buttons
Pressing the corresponding air distribution button enables the various vent openings to be selected. The display of each selected setting is indicated by LEDs in the buttons.

Air volume selector wheel
The air volume can be manually set by turning the air volume selector wheel. The selected setting is displayed by LEDs around the circumference of the selector wheel.

Controls with code (581) Comfort automatic air conditioning
^ "AUTO" button
^ "ZONE" button (without code (494) USA version)
^ "MAX COOL" button (with code (494) USA version)
^ "A/C and REST" button (without code (494) USA version)
^ "A/C" button (with code (494) USA version)
^ Air distribution button
^ Air volume buttons
^ "OFF" button

"AUTO" button
The air volume and the air distribution are controlled automatically when the "AUTO" button is pressed. If automatic mode is activated, the LED comes on.

"ZONE" button (without code (494) USA version)
When the "ZONE" button is pressed, the values set on the driver side are adopted for the passenger side.

"MAX COOL" button (with code (494) USA version)
Pressing the "MAX COOL" button raises the blower output to 100%. The specified temperature values are regulated to "Maximum cold".
"MAX COOL" is shown on the display.

"A/C and REST" button (without code (494) USA version)
Pressing the "AC and REST" button activates the residual engine heat utilization function or switches the A/C compressor on or off depending on the circuit 15 status.

"A/C" button (with code (494) USA version)
Pressing the "A/C" button when the engine is running switches the A/C compressor on or off. All other functions are retained. The LED lights up when the refrigerant compressor is switched on.

Air distribution button
The desired air distribution can be set by pressing the air distribution button. The selected air distribution setting is shown on the display.

Air volume buttons
The air volume can be manually set by pressing the air volume button. The selected setting is shown on the display.

"OFF" button
The automatic air conditioning can be switched off completely or switched back on by pressing the "OFF" button.

Reading in of sensors and signals
The input factors are read in via the following connections:
^ Direct line
^ Climate control LIN (LIN B8)
^ Interior CAN (CAN B)

Direct line
The following sensors are read in via a direct line:
- Interior temperature sensor (B10/4) (with code (581) Comfort automatic air conditioning)
- Evaporator temperature sensor (B10/6)
- Left footwell vent air outlet temperature sensor (B10/35)
- Right footwell vent air outlet temperature sensor (B10/36) (with code (581) Comfort automatic air conditioning)
- Sun sensor (B32/3) (with code (581) Comfort automatic air conditioning)
- Interior temperature sensor with integrated fan (N70b1)

Climate control LIN
The following sensor is read in via climate control LIN:
- Air quality sensor (B31) (with code (581) Comfort automatic air conditioning)

Interior CAN
The signals are read in by the control and operating unit via the interior CAN.
The functions resulting therefrom are described in the corresponding function descriptions (see block diagram or function schematic).

Evaluation of input factors
The input factors that have been read in are evaluated by the integrated microprocessor and the affected components are then actuated.

Component actuation
Components are actuated via the following lines:
^ Direct line
^ Climate control LIN
^ Interior CAN

Direct line
The following component is actuated via a direct line:
- Blower regulator (A32n1)

Climate control LIN
The following components are actuated via climate control LIN:
- Fresh air/recirculated air flap actuator motor (M2/5)
- Left blend air flap actuator motor (M2/6) (with code (581) Comfort automatic air conditioning)
- Right blend air flap actuator motor (M2/7) (with code (581) Comfort automatic air conditioning)
- Blend air flap actuator motor (M2/14) (without code (581) Comfort automatic air conditioning)
- Defroster flap actuator motor (M2/16)
- Center air outlet flap actuator motor (M2/22)

Interior CAN
The signals are transmitted by the control and operating unit via the interior CAN.
The functions resulting therefrom are described in the corresponding function descriptions (see block diagram or function schematic).




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