I read in my manual and other posts on t'interweb about auxillary heaters, not the Webasto fuel burner, definately not got one of those, but manual says if I press the windscreen button, and I'm sure it mentions the word 'heater' to demist the windscreen.

Does the A4 (mine is a 1.9TDI Avant SE) have a heat booster when the engine is cold?
From experience the Windscreen button just tends to put max blower and full on windscreen setting with ECON off.

Just wondering.