Automatic Air Conditioning (AAC), Function

GF83.40-P-0001T Automatic Air Conditioning (AAC), Function
- except CODE (581) Comfort automatic air conditioning


Overall description
The automatic air conditioning (AAC) controls the equipment to achieve the interior temperature desired by the driver and passengers. The automatic air conditioning is available immediately after starting the engine. The system operates on the basis of the humidity and temperature. The ambient air is first cooled down by adding cooled air from the evaporator, even at low outdoor temperatures and then passes through the heat exchanger where it is heated up to the desired temperature.

The automatic air conditioning regulates the interior temperature and air distribution separately for the driver and passenger seats.

The system has the following sub-functions:

^ Heater circuit
The coolant is heated up by the engine. When heat is requested, heated coolant passes through the heat exchanger shutoff motor (M16/32) to the heater heat exchanger, where heat is dissipated to the interior air. The coolant returns back to the coolant pump via the heater return.

^ Refrigerant circuit
The refrigerant compressor (A9) driven by the engine compresses the refrigerant vapor which is cooled down in the condenser. The refrigerant liquefies during cooling. The liquid refrigerant passes through the expansion valve into the evaporator, where it evaporates, cools down and removes the heat from the air that is flowing past, therefore cooling it down. The refrigerant compressor (A9) draws in the coolant which has turned gaseous through the collection of heat and compresses it again.

^ Ventilation
The ventilation system ventilates the interior of the vehicle. The air is drawn in by the blower motor (A32m1) and passes through the various air ducts to the air distribution flaps which distribute it in the vehicle interior.

^ Control
The electronic control for the automatic air conditioning is accomplished by various control units and temperature sensors connected with one another by the Control Area Network bus, class B (interior compartment) (CAN B), Control Area Network bus, class C (engine compartment) (CAN C) and Local Interconnect Network (LIN). The desired temperature is achieved or maintained at a constant level by cooling or heating the air.

^ Residual engine heat utilization
The residual engine heat utilization feature makes it possible to continue to heat or simply ventilate the vehicle even with the engine shut off. The system makes use of the residual heat of the engine for this purpose.

^ Solar stationary ventilation
(Model 211.0 with code (419) Solar module for panoramic glass roof)
The solar stationary ventilation ensures air circulation in the vehicle. Solar energy obtained by the solar cells operates the blower motor (A32m1) via the blower regulator (A32n1) and supplies ambient air into the vehicle interior.

This reduces the high temperatures in the passenger compartment. Air circulation increases along with any increase in solar radiation.