GF83.40-P-0004RT Convenience Automatic Air Conditioning (C-AAC), Function
GF83.40-P-0004RT Convenience Automatic Air Conditioning (C-AAC), Function
- with CODE (581) Comfort automatic air conditioning
- with CODE (582) Rear air conditioner
Function
The comfort automatic air conditioning (C-AAC) controls the interior temperature desired by the driver and the passengers. The comfort automatic air conditioning is operational immediately after the engine is started and produces the last stored temperature- controlled condition before the vehicle was locked. System operation is sensitive to humidity 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 C-AAC [K-KLA] controls the interior temperature separately for all 6 seats.
The comfort automatic air conditioning can be summarized with the subfunctions listed below:
^ Heating circuit
The coolant is heated up by the engine. When heat is required, heated coolant passes through the heating system heat exchanger where heat is transferred to the interior air. The coolant returns back to the coolant pump via the heater return. The rear air conditioner is assisted by the rear AC additional circulation pump.
^ Refrigerant circuit
The refrigerant compressor (AC compressor) driven by the engine compresses the gaseous refrigerant, which is thereby heated up and routed to the condenser. The refrigerant's compression heat is then withdrawn on the surface of the condenser. The refrigerant liquefies when it cools down. Chemical and mechanical impurities are removed from the refrigerant in the downstream fluid reservoir.
After cleaning, the liquid refrigerant is injected into the evaporator located in the fresh air flow. The refrigerant evaporates and cools down. Through this evaporation process heat is extracted from the fresh air flowing past from outside over the tube and fin system so that air cools down. The air humidity carried along is converted to condensed water, which is routed to the outside. The air is thus dried. The refrigerant compressor aspirates the refrigerant which has turned gaseous on account of the heat absorption and then compresses it yet again.
If required, the engine fan is switched on as well in the process. Cool air can be routed into the passenger compartment through the various air vents when the engine is running and the blower switched on.
The degree of cooling intensity is dependent upon the previously set in-car temperature and the blower output. A second evaporator is added to the refrigeration circuit in the form of the rear air conditioner.
^ Ventilation
The ventilation system ventilates the interior of the vehicle. During normal operation, when the vehicle is stationary or in order to increase the air volume, ventilation is carried out with the assistance of the "front blower", the "booster blower" and also a "rear blower" belonging to the C-AAC. The air is led through various air ducts to the air distribution vents, through which it is distributed in the vehicle interior.
^ Control
The comfort automatic air conditioning is controlled electronically via various control units and temperature sensors, which are interconnected via the Controller Area Network bus class B (interior) (CAN-B), the Controller Area Network Bus Class C (engine compartment) (CAN-C), and the local interconnect network (LIN). The desired temperature is achieved or maintained at a constant level by cooling or heating the air.
^ Engine residual heat utilization system
The residual engine heat utilization makes it possible to heat or only ventilate the vehicle even when the engine is switched off. To do so the system utilizes the residual heat from the engine and guides it via the blower into the passenger compartment.
The residual engine heat utilization feature is possible only when the ignition is "OFF".
^ Defrosting function
The defrosting function serves for keeping the windows free of fog and ice or quickly eliminating fogged windows by actuating the defroster outlet flap to the full open position and closing the footwell flaps. Additionally, the refrigerant compressor is cut in, the fresh air flap is set to fully open and the coolant circulation pump (M13) and the rear AC additional circulation pump (M13/1) as well as the PTC heater booster (R22/3) (on diesel engines) are actuated.
^ AC-OFF function
This function blocks the refrigerant compressor's cut-in. This takes place manually when the button on the comfort AAC [KLA] control and operating unit (N22/7) is pressed. The active AC OFF function is displayed by an LED.
^ Recirculated air, function
When the air recirculation switch (N22s2) is actuated momentarily (t < 1.5 s), the fresh air supply is interrupted from outside by closing the fresh and air recirculation flap.This causes the air to circulate (closed windows and sliding roof assumed) in the interior only and keeps unpleasant odors or pollutants at bay. The function LED is illuminated during operation. The comfort automatic air conditioning is equipped with an automatic recirculation control.
^ Remote control for rear AC functions
When the REAR button on the comfort AAC control and operating unit (N22/7) is pressed, the operating unit symbol appears in the front display.The blower setting is not visible. The rear temperatures can be set on the keyboard.
The function is stopped automatically, if operation is not performed within approx. t = 5 s or the REAR button is pressed again.When the AUTO button or the REAR Button is pressed, the REAR operation can be stopped.
^ Emission-controlled recirculated air, function
The emissions sensor (B31) transmits the pollutant values of the ambient air to the comfort AAC control and operating unit. The comfort AAC control and operating unit decides on the position of the air recirculation flap together with the dew point sensor (B11/12).
This function is not available with A/C OFF.
OFF function
The air conditioning is switched off, the flap positions are maintained.
^ Recirculated air convenience feature function
For easier operation, the windows and the tilting/sliding roof (SHD) (with power glass tilting/sliding roof, code 414) or the panoramic sliding roof (with panoramic sliding roof, code 413) are closed automatically when the air recirculation switch (N22/7s2) is pressed for more than 1.5 s. If the air recirculation switch is actuated again, the windows, the tilting/sliding roof (SHD) and the panoramic sliding roof automatically return to their previous positions.
The left vent window motor (M21/8) and right vent window motor (M21/9) are actuated via recirculated air convenience feature.
^ AUTO button, function
When the AUTO button is actuated, the AUTO mode is activated and the red LED in the AUTO button comes on. In automatic mode, the blower output and air distribution are controlled automatically, in addition to temperature control. Manually resetting the blower or the air distribution, terminates the AUTO mode. When the vehicle is restarted, the function last set is activated.
The blower level is higher on the US version than on the ECE version.In the event of maximum cooling output, "MAX COOL" is additionally shown in the USA version.
