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GF83.40-P-0005LEH Automatic Air Conditioning, Function



GF83.40-P-0005LEH Automatic Air Conditioning, Function

Function requirements, general
^ Circuit 15 ON (operational functions, heater, ventilation)
^ Circuit 15C ON or circuit 15R ON (residual heat)
^ Circuit 61 ON (cooling)

Status of circuit 15 is provided by EIS [EZS] control unit (N73) via interior CAN (CAN B).
The status of circuit 61 is provided by the ME-SFI [ME] control unit (N3/10) via chassis CAN (CAN E) and forwarded from central gateway control unit (N93) via interior CAN to AAC [KLA] control unit (N22/1).

Circuit 61 is required to start the electric refrigerant compressor (A9/5). Then cooling is possible even without engine speed (stop mode).

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 (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 each performed 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
^ Function sequence of air conditioning operation in stop mode

Further partial functions are described in separate documents:
^ Automatic air conditioning refrigerant circuit, function
^ Ventilation system, function
^ Regulation of Automatic air conditioning, function
^ Battery cooling system, 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 for rear air conditioning
(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:
- Switching on and off of electric refrigerant compressor
- 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 for rear air conditioning
(with code (582) Rear air conditioning)

The settings performed via front central operating unit are shown in the COMAND display (A40/8) (without code (867) SPLITVIEW) or in the 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.

To achieve the operating temperature more quickly with a cold engine, the ME-SFI [ME] control unit can close off the coolant circuit to the heating system by actuating the heating system shutoff valve (Y16/2).
With the heater switched on ("Heating" status of the AAC [KLA] control unit), the heating system shutoff valve is always open.

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 ON or circuit 15R ON

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. 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, 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.

If the rear air conditioning residual engine heat utilization is active, it is not possible to manually select the temperature or the blower output at 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 status: circuit 15 ON
- the timer stops
- the on-board electrical system voltage is low
- The OFF/residual heat button or the "OFF" button at the AAC [KLA] control unit is pressed
- With code (582) Rear air conditioning
- The right air distribution/REST button on the rear air conditioning control unit is pressed
- 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
^ Air conditioning was active at least once during the ignition sequence
^ Evaporator temperature must be cooled to a great extent
^ Engine OFF (circuit 61 OFF)
^ Doors closed
^ Kilometer reading > 250 km

Function sequence for evaporator drying process
To counteract any evaporator odor in the interior and any fogging of windows when starting the air conditioning, an evaporator drying process is conducted at the air conditioning system.
With circuit 61 OFF, the timer is activated in the instrument cluster (A1). The circuit status is sent from the ME-SFI [ME] control unit via chassis CAN to the central gateway control unit and further via central CAN to the instrument cluster.

Following a waiting time of t = 40 min, the instrument cluster sends the request for evaporator drying via central CAN to the central gateway control unit. This sends the request via interior CAN to the AAC [KLA] control unit, which starts the evaporator drying. To this end the blower is activated at the lowest setting for t = 30 min.
The AAC [KLA] control unit sends the request of the blower via the climate control LIN to the blower regulator. The blower regulator actuates the blower motor at the lowest blower stage.

Function sequence of air conditioning operation in stop mode
Under the precondition that the coolant temperature is sufficiently warm, the high-voltage battery (A100g1) has a sufficient charge level and the specified temperature of the heating system has been reached, the engine is stopped as soon as the vehicle speed falls below a specified speed while braking.

The stop mode function sequence consists of the following subfunctions:
^ Function sequence for cooling mode
^ Function sequence, heating mode

Function sequence for cooling mode
The air conditioning can also be operated to a limited extent of time in stop/start mode with the engine switched off thanks to the electric refrigerant compressor. The duration of the air conditioning operation during this type of stop phase can last up to several minutes depending on the cooling output requirement and charge level of the high-voltage battery.
To maximize the duration of the engine stop, the air conditioning is operated with reduced cooling output (i.e. reduced power consumption of the electric refrigerant compressor, the engine and air conditioning electric suction fan with integrated control (M4/7), the blower regulator and the rear air conditioning electronic blower regulator) if necessary.

At high outside temperatures, air recirculation mode is automatically selected (light-emitting diode in air recirculation button (N72/1s37) remains switched off).
If the lowest electrical charge threshold of the high-voltage battery that still enables the engine to be started is reached, the engine automatically switched on again. For reasons of convenience, the rpm of the electric refrigerant compressor is oriented toward the output of the interior blower and the ground speed.

Function sequence, heating mode
The heating comfort in the interior is maintained in stop/start mode. The duration of the engine stop in heating mode depends on the ambient temperature, the coolant temperature and the heating requirement.
As soon as the desired temperature can no longer be maintained in the interior, the engine is started.