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

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

Automatic air conditioning, general
Two different automatic air conditioning versions are installed:
- Standard automatic air conditioning with 2-zone temperature control
(without code (581) Comfort automatic air conditioning)
- Comfort automatic air conditioning with 3-zone temperature control (with code (581) Comfort automatic air conditioning) without and with rear air conditioning
(model 164.8 and model 251 with code (582) Rear air conditioning)

The automatic air conditioning without code (581) Comfort automatic air conditioning is equipped with a separate temperature control for the driver side and the front passenger side. 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 separate temperature control for the driver side and the front passenger side and for the rear compartment.
Front and rear blower control takes place with 2 zones and can be operated manually or controlled automatically.

The cooling and heat output is increased in the rear area by the rear air conditioning (model 164.8 and model 251 with code (582) Rear air conditioning).

The regulation and control are carried out by the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or by the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning).

The automatic air conditioning comprises the following subfunctions:
^ Heating circuit function sequence
^ Residual engine heat utilization function sequence
^ Function sequence for evaporator drying process (as of 1.9.08)

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 is directed through the heater heat exchanger and the rear air conditioning heater heat exchanger (model 164.8 and model 251 with code (582) Rear air conditioning), which deliver the heat to the air blowing by.
Additionally, at low engine rpm, the coolant circulation pump (M13) is actuated to ensure that the flow volume needed to heat up the air blowing by is adequate.
The heater circulation pump is directly actuated by the control and operating unit.

Function requirements, residual engine heat utilization
^ Circuit 15C or circuit 15R ON

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

Residual engine heat utilization function sequence
Pressing the REST button on the control and operating unit switches on the residual engine heat utilization function.. The control and operating unit actuates the heater circulation pump directly. The coolant circulation pump delivers the coolant (residual heat) that is still warm through the heater heat exchanger. The control and operating unit forwards the ventilation request to the blower regulator (A32n1) at the same time, whereupon the blower motor (A32m1) is actuated at slow speed by the blower regulator.

The air drawn in by the blower motor is routed along the heater heat exchanger and thus heated up.
The function stops after approx. t = 30 min.
If the on-board electrical system voltage drops below a certain value, the function is automatically switched off by the on-board electrical system management system.

Function requirements, evaporator drying process (as of 1.9.08)
^ Air conditioning was active at least once during the ignition sequence
^ Evaporator temperature T > 3 °C
^ Engine off (circuit 61 off)
^ Doors closed
^ Kilometer reading > 250 km

Function sequence for evaporator drying process (as of 1.9.08)
In order to counteract any evaporator odor in the interior and any fogging of the windows when starting the air conditioning system, an evaporator drying process is executed on the front air conditioning and the rear air conditioning (for model 164.8 and model 251 with code (582) Air conditioning system in rear). At circuit 61 Off the timer in the instrument cluster (A1) is activated.
The status of circuit 61 is placed on the engine compartment CAN (CAN C) by the CDI control unit (N3/9) (with diesel engine) or by the ME-SFI [ME] control unit (N3/10) (with gasoline engine).

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 sends the blower request over the climate control LIN (LIN B8) to the blower regulator (A32n1) and on model 164.8 and model 251 with code (582) Air conditioning system in the rear to the rear air conditioning blower regulator (N29/7). The blower regulator actuates the blower motor and the rear air conditioning blower regulator actuates the rear air conditioning blower motor (M2/29), at the lowest blower setting in each case.