Either the auxiliary heating or the auxiliary ventilation is switched on, depending on the ambient temperature and the temperature selected on the air conditioner console.
The auxiliary heating heats the Audi A4 interior and defrosts the windows. It can be used when the Audi A4 is stationary and when driving (to provide extra heat while the engine is warming up). The auxiliary heating runs on fuel.
The auxiliary ventilation cools and ventilates the Audi A4 interior.
Conditions for operation
- The fuel gauge is above the reserve zone
- The battery is adequately charged
- The temperature inside the Audi A4 differs from the temperature setting on the console.
WARNING!
- The auxiliary heating must not be allowed to run when the Audi A4 is in a confined space because it can give off toxic fumes.
- To avoid any possible fire risk, never have the auxiliary heating switched on when refuelling the Audi A4.
- Because of the high temperatures which occur when the auxiliary heating is running, make sure when parking the car that the exhaust outlet under the car is not obstructed in any way and that the exhaust gases do not come into contact with flammable materials (fire risk).
Note
- It is advisable to open the air outlets on the dashboard when using the auxiliary heating/ventilation.
- The indicator lamp
(auxiliary heating) or 
(auxiliary ventilation) flashes in the instrument cluster display when the auxiliary heating/ventilation is switched on. Both indicator lamps light up continuously when a timer is activated. - At low outside temperatures, some visible water vapour may form in the engine compartment. This is no cause for concern.