GF83.40-P-0005FL Automatic Air Conditioning, Function
GF83.40-P-0005FL Automatic Air Conditioning, Function
Function requirements, general
^ Control functions: circuit 15 ON
^ Climate control: circuit 61 ON
The electronic ignition lock control unit (N73) transmits the circuit status of circuit 15 to the interior CAN (CAN B). Circuit status c. 61 is provided by the CDI control unit (N3/9) (with diesel engine) or ME-SFI control unit (N3/10) (with gasoline engine) to the chassis CAN (CAN E) and routed by the front SAM control unit with fuse and relay module (N10/1) to the interior CAN.
Automatic air conditioning, general
Two different automatic air conditioning versions are installed:
- Automatic air conditioning with 2-zone temperature control
(without code (581) Comfort automatic air conditioning)
- Automatic air conditioning with 3-zone temperature control
(with code (581) Comfort automatic air conditioning)
Regulation and control are performed by the automatic air conditioning control and operating unit (N22/7).
The automatic air conditioning without code (581) Comfort automatic air conditioning is equipped with a separate temperature control for the left and the right half of the vehicle. Blower control takes place with 1 zone and can be operated manually or controlled automatically.
The automatic air conditioning with code (581) Comfort automatic air conditioning is equipped with a separate temperature control for the left and the right half of the vehicle and for the rear compartment.
The front blower control can be manually or automatically operated. Manual operation is only possible in the rear using a separate rear automatic air conditioning operating unit (N22/4). The blower is controlled in 2 zones (front and rear).
The automatic air conditioning function consists of the following subfunctions:
^ Heating circuit function sequence
^ Function sequence for residual heat mode (with code (581) Comfort automatic air conditioning or with code (965) Electrical preinstallation for rental vehicle)
^ Function sequence for evaporator drying process
Further subfunctions are described in separate documents:
^ Automatic air conditioning refrigerant circuit, function
^ Ventilation system, function
^ Regulation of Automatic air conditioning, function
Heating circuit function sequence
Driven by the coolant pump, the coolant circulates in the engine cooling circuit. In the process, it absorbs engine heat. The heated coolant passes through the heater heat exchanger, which dissipates heat to the air blowing by.
At low engine rpm the coolant circulation pump (M13/5) (with code (581) C-AAC or with code (965) Electrical preinstallation for rental vehicle) is also actuated to ensure that the flow rate to heat the air flowing past is sufficient. The coolant circulation pump is actuated by the front SAM control unit on request of the control and operating unit.
Function sequence for residual heat mode (with code (581) Comfort automatic air conditioning or with code (965) Electrical preinstallation for rental vehicle)
Pressing the "REST" button (with code (581) Comfort automatic air conditioning) or the "A/C, REST" button (without code (581) Comfort automatic air conditioning and with code (965) Electrical preinstallation for rental vehicle) on the control and operating unit switches on the function. The control and operating unit transmits the request over the interior CAN to the front SAM control unit, which directly actuates the coolant circulation pump. The coolant circulation pump delivers the still warm (residual heat) coolant through the heat exchanger.
At the same time, the control and operating unit sends the ventilation request to the blower regulator (A32n1), which then actuates the blower motor (A32m1) at reduced power. The air drawn in by the blower motor is routed along the heater heat exchanger and thus heated up.
The function is terminated after a time of t = 30 min. has elapsed or when the on-board power supply voltage drops below a certain value.
Additional function requirements for evaporator drying process
^ Air conditioning was active at least once during the ignition sequence
^ Evaporator temperature T > 3 °C
^ Engine OFF (c. 61 OFF) (provided by CDI control unit or ME SFI control unit)
^ 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 in the instrument cluster (A1) is activated. The circuit status is read in by the CDI control unit or by the ME-SFI [ME] control unit over the chassis CAN and sent to the instrument cluster.
After a waiting time of t = 1 h the instrument cluster sends the request for the evaporator drying process via the interior CAN to the control and operating unit which then starts the evaporator drying process. To this end the blower is activated at the lowest setting for t = 30 min.
The control and operating unit transmits the request from the blower directly to the blower regulator. The blower regulator actuates the blower motor at the lowest blower stage.
During the evaporator drying function sequence, the LED in the "REST" button (with code (581) Comfort automatic air conditioning) or the "A/C, REST" button (without code (581) Comfort automatic air conditioning and with code (965) Electrical preinstallation for rental vehicle) in the control and operating unit lights up, as does the function indicator in the stationary heater button (N72/1s30), with code (228) Stationary heater, in the upper control panel control unit (N72/1).
