Convenience Automatic Air Conditioning (C-AAC), Function

GF83.40-P-0004P Convenience Automatic Air Conditioning (C-AAC), Function

MODEL 203.0 /2 /7 up to 31.5.01
- with CODE (581) Automatic air conditioning
MODEL 203.0 /2 /7 as of 1.6.01
- with CODE (581) Comfort automatic air conditioning
- up to Model Year 8

Function
The comfort automatic air conditioning (C-AAC) regulates the desired passenger compartment temperature in accordance with the driver or passenger needs in terms of heating, cooling and air distribution. The air conditioning is fully operational after starting the engine and restores the last stored temperature status before locking the vehicle. System operation is sensitive to moisture and temperature; even at low outside temperatures the ambient air is first cooled down by way of the evaporator's supply of cold air, and then routed through the heat exchanger and set to the desired passenger compartment temperature. The comfort automatic air conditioning (C-AAC) controls the interior temperature and the air distribution separately for the driver and passenger sides.

The comfort automatic air conditioning (C-AAC) can be summarized under the following list of sub-functions.

- Ventilation
Ventilation ensures aeration in the vehicle interior. Ventilation is achieved with the support of the blower motor (A32m1) during normal operation, when vehicle is stationary or to increase the air flow. The air is distributed in the vehicle interior via air distribution flaps.

In order to prevent window fogging, the footwell flaps are opened fully for 30 seconds after the ignition has been switched on. When the ignition is switched off, the fresh air/air recirculation flap is automatically moved into a 50 % fresh air and 50 % air recirculation position. This achieves a significant reduction in the flap closing forces.

- Heater circuit
Coolant is heated via the engine. The heated coolant is subsequently guided through the heat exchanger, where the heat is emitted into the air in the interior. Via the heater return, which contains the hot water recirculation pump (M13), the coolant is returned to the coolant pump. The hot water recirculation pump (M13) ensures that the coolant is circulated.
The coolant flows through the heating system heat exchanger permanently. Depending on the required in-car temperature, control takes place using the blending air flaps, which are activated separately for the left and right sides by the left blending air flap actuator motor (M2/6) and the right blending air flap actuator motor (M2/7).

- Refrigerant circuit
The refrigerant compressor (A9) compresses the refrigerant vapor which is heated up during the process, routed into the condenser and thus cooled down. After being cleaned in the fluid reservoir, the liquid refrigerant is injected into the evaporator. The refrigerant evaporates and cools down. The refrigerant compressor (A9) again intakes the refrigerant, which has returned to its gaseous form as a result of heat absorption.

- Comfort automatic air conditioning (C-AAC) control
The electronic control of the comfort automatic air conditioning (C-AAC [K-KLA]) takes place using various control units that are interconnected via the class B (interior) Controller Area Network Bus (CAN-B). The CAN-B is a bi-directional bus, i.e. each connected control unit receives and transmits information.

- Comfort automatic air conditioning (C-AAC) temperature control
The desired temperature is achieved or maintained at a constant level by cooling or heating the air. An exact temperature control is achieved by the reading in various temperature sensors.

- Residual engine heat utilization
Residual engine heat utilization enables the vehicle to be heated even when the ignition is OFF. To do so the system utilizes the residual heat from the engine and leads it into the passenger compartment via the blower motor (A32m1). The hot water recirculation pump (M13) ensures that the coolant is circulated.