The basic settings for the air conditioner can be adjusted via the infotainment system.
Select: Function selector button CAR > control button AC. Or:
Select: Function selector button CAR > control button Car systems* > AC.
Automatic air recirculation*
Air recirculation is controlled automatically when this function is activated. If the windows mist up, press the 
FRONT button.
FRONT button.Synchronisation*
When synchronisation is activated, all the driver's settings (with the exception of seat heating/ventilation*) are applied to the front passenger's seat. The synchronisation is deactivated as soon as any adjustments are made on the front passenger's side.
The settings can also be synchronised by pressing and holding the rotary control on the driver's side.
Supplementary heater*
The supplementary heater warms up the interior of Audi A4s with a diesel or flexible fuel engine more quickly. When set to auto, the supplementary heater is controlled automatically.
For the sake of the environment
The automatic air conditioner runs in a particularly economical mode when the efficiency* setting is selected (Link).