Automatic air conditioning, function - GF83.40-P-0005LE

MODEL 216.3, 221.0 /1 (except, 221.095 /195) as of Model Year 2009 /Modification Year 08 

Function requirements, general 

• C. 15 On (control functions, heater, ventilation)
• C. 15C On or c. 15R On (residual heat)
• C. 61 On (cooling)

The circuit status of circuit 15 is provided by the EIS [EZS] control unit (N73) on the interior CAN (CAN-B).

The circuit status of circuit 61 is made available on the chassis CAN (CAN E) by the CDI control unit (N3/9) (for diesel engine) or by the ME-SFI [ME] control unit (N3/10) (for gasoline engine) and forwarded from the central gateway control unit (N93) via the interior CAN to the AAC [KLA] control unit (N22/1).

Automatic air conditioning, general 

Two different automatic air conditioning versions are installed:

• Automatic air conditioning with 4-zone temperature control (without code (582) Rear air conditioning)
• Automatic air conditioning with 6-zone temperature control (model 221 with code (582) Rear air conditioning)

The automatic air conditioning with 4-zone temperature control is equipped with a separate temperature control for the left and the right side of the vehicle. The footwell temperature can be adjusted separately. Blower control takes place with 2 zone and can be operated manually or controlled automatically.

The automatic air conditioning with 6-zone temperature control is equipped both at the front and in the rear area with a separate temperature control for the left and the right side of the vehicle.

The front blower control takes place in 2 zones and can be operated manually or controlled automatically. The blower control in the rear area takes place in 1 zone.

The regulation and control are performed in each case by the AAC [KLA] control unit.

The automatic air conditioning function consists of the following subfunctions:

• Operation function sequence 
• Heating circuit function sequence 
• Residual engine heat utilization function sequence 
• Function sequence for evaporator drying process (as of 1.6.09) 

Further subfunctions are described in separate documents:

• Automatic air conditioning refrigerant circuit, function 
• Ventilation system, function 
• Regulation of Automatic air conditioning, function 

Operation function sequence 

The AAC [KLA] control unit can be operated via the upper control panel control unit (N72/1), via the front central operating unit (A40/9) or via the rear air conditioning control unit (N22/4) (with code (582) Rear air conditioning).

The upper control panel control unit permits the following operations:

• Switching the automatic air conditioning on and off
• Separate interior temperature selection
• Separate blower setting
• Separate overall automatic function
• Defrost function
• Residual engine heat utilization system
• Recirculated air mode
• Remote control of rear air conditioning (model 221 with code (582) Rear air conditioning)
• Heated rear window (R1) actuation
• Control of stationary heater (with code (228) Stationary heater)

The front central operating unit permits the following operations:

• Switch refrigerant compressor (A9) on and off
• Separate interior temperature selection
• Separate blower setting
• Separate air distribution
• Setting of the air flow to
  • focused (strong air flow)
  • medium (default setting)
  • diffused (weak air flow)
• Adaptation of the footwell temperature
• Coupling of all setting zones with driver zone "MONO"
• Remote control of rear air conditioning (model 221 with code (582) Rear air conditioning)

Settings made on the central front operating unit are indicated on the COMAND display (A40/8) (without code (867) SPLITVIEW) or in SPLITVIEW display (A40/10) (with code (867) SPLITVIEW).

The rear AC control unit allows the following operations:

• Separate interior temperature selection
• Separate preselection of the air distribution
• Air volume setting
• Residual engine heat utilization system activation

• "AUTO" (automatic mode)
• "MAN" (manual mode)
• "OFF" (switching off of rear air conditioning)

Heating circuit function sequence 

Driven by the coolant pump, the coolant circulates in the engine cooling circuit. In the process, it absorbs engine heat. When heating is requested, the air conditioning water valve (Y19/2) is opened. The heated coolant passes through the heater heat exchanger, which dissipates heat to the air blowing by.

The heater circulation pump (M13) is also actuated in heating mode. This ensures that the flow volume is adequate for heating the passing flow of air. The air conditioning water valve and the heater circulation pump are actuated by the front SAM control unit with fuse and relay module (N10/1), which receives the request from the AAC [KLA] control unit via the interior CAN.

On model 221 with code (582) Rear air conditioning, the heated coolant is also delivered through the rear air conditioning heater heat exchanger. The supply to the heater heat exchanger is controlled by the rear auxiliary heating system supply unit (A31/1) via the integrated left duovalve (A31/1y1) and the right duovalve (A31/1y2).

The rear heating system feed unit is actuated directly by the AAC [KLA] control unit.

Additional function requirements for residual engine heat utilization 

• Circuit 15C or circuit 15R

Residual engine heat utilization function sequence 

The residual engine heat utilization function is switched on by pressing the REST button (without code (228) Stationary heater) or the OFF/residual heat button (N72/1s38) (with code (228) Stationary heater) on the upper control panel control unit. The upper control panel control unit transmits the request to the AAC [KLA] control unit via the interior CAN.

The AAC [KLA] control unit transmits the switch-on request via the interior CAN to the front SAM control unit. This actuates the heater circulation pump. The coolant circulation pump delivers the coolant (residual heat) that is still warm through the heater heat exchanger.

On model 221 with code (582) Rear air conditioning there is a separate rear air conditioning residual engine heat utilization function. This is switched on by the right air distribution/REST button in the rear air conditioning control unit.

The corresponding request is forwarded via the telematics CAN (CAN A) to the COMAND controller unit (A40/3), transferred via the central CAN (CAN F) to the central gateway control unit and from there via the interior CAN to the AAC [KLA] control unit.

The AAC [KLA] control unit directly actuates the circulation pump (A31/1m1) integrated into the rear heating system feed unit. The circulation pump delivers the coolant that is still warm (residual heat) through the rear air conditioning heater heat exchanger. The AAC [KLA] control unit at the same time transmits the ventilation request via the climate control LIN (LIN B8) to the blower regulator (A32n1) and, on model 221 with code (582) Rear air conditioning, to the rear air conditioning electronic blower regulator (N29/2). The blower regulator actuates the blower motor (A32m1) and the rear air conditioning electronic blower regulator actuates the rear blower motor (M2/1) each at a reduced output.

When the rear air conditioning is switched to the residual engine heat utilization mode, it is not possible to select the temperature or blower output manually on the rear air conditioning control unit.

The air drawn in by the particular blower motor is routed along the assigned heater heat exchanger and thus heated up.

The residual engine heat utilization function is terminated by the following events:

• Circuit 15 On status
• the timer stops
• the on-board electrical system voltage is low
• Actuation of OFF/residual heat button or "OFF" button on AAC control unit
• On model 221 with code (582) Rear air conditioning

• Actuation of right air distribution/residual button on rear air conditioning control unit
• The system is switched off manually by pressing the function mode button on the rear air conditioning control unit until the "OFF" mode is reached

Additional function requirements for evaporator drying process (as of 1.6.09) 

• Air conditioning was active at least once during the ignition sequence
• The evaporator temperature must have decreased significantly
• Engine off (circuit 61 off)
• Doors closed
• Kilometer reading > 250 km

Function sequence for evaporator drying process (as of 1.6.09) 

To counteract any evaporator odor in the interior and any fogging of windows when starting the air conditioning, an evaporator drying process is performed in the air conditioning system.

At circuit 61 Off the timer in the instrument cluster (A1) is activated. The circuit status is transmitted by the CDI control unit or ME control unit via the chassis CAN to the central gateway control unit and relayed via the central CAN to the instrument cluster.

After a waiting time of t = 40 min, the instrument cluster sends the request for evaporation drying to the central gateway control unit via the central CAN. The latter sends a request via the interior CAN to the AAC control unit which starts evaporator drying. To this end the blower is activated at the lowest setting for t = 30 min.

The AAC control unit sends the request for the blower to the blower regulator via the air conditioning LIN. The blower regulator actuates the blower motor at the lowest blower stage.