Automatic Air Conditioning (AAC) Function

GF83.40-P-0001R Automatic Air Conditioning (AAC) Function


Function
The automatic air conditioning (AAC) is equipped with an electronically controlled cooling, heating and ventilation system, and can be summarized in the sub-functions listed below:

^ Ventilation
Ventilation ensures aeration in the vehicle interior. In the normal mode, when the vehicle is stationary or in order to increase the air flow, the ventilation of the interior is achieved with assistance of the blower. 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/recirculated air flap is closed (100 % fresh air).

^ Automatic air conditioning temperature control
The desired temperature is achieved or maintained at a constant level by cooling or heating the air. Precise temperature control is achieved by reading various temperature sensors in.

^ Automatic air conditioning control
Automatic air conditioning electronic control is carried out via various control units, which are interconnected via the CAN data bus (CAN-B). The CAN data bus is a bi-directional bus, i.e., each connected control unit receives and transmits information.

^ AAC pushbutton control unit (N22)
The automatic air conditioning can be operated by the driver via the actuation of various function buttons. The AAC pushbutton control unit (N22) additionally reads in various sensor signals, processes these and activates automatic air conditioning components.

^ Residual engine heat utilization
Residual engine heat utilization enables the vehicle to be heated even when the ignition is OFF. In order to achieve this, the system utilizes the residual heat from the engine, and guides this into the passenger compartment via the blower. The hot water recirculation pump (M13) ensures that the coolant is circulated.

^ 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.
The hot water recirculation pump (M13) ensures that the coolant is circulated.
Via the heater return, which contains the hot water recirculation pump (M13), the coolant is returned to the coolant pump. The flow of coolant to the heat exchanger is regulated by the heat exchanger shutoff motor (M16/32).
Temperature control, depending on the temperature desired in the vehicle interior, is carried out via the blending air flaps, which are activated - separately for the left and right side - via the blending air flap actuator motors.

^ Refrigerant circuit
The refrigerant compressor (A9) compresses the gaseous refrigerant, which is thereby heated, guided into the condenser and then cooled. 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.