The pictogram for the windshielf is for defrosting. Defrosting requires maximum air flow, so leave that one alone unless you want maximum fan speed. Think of it as a shortcut key on a computer. If it takes you to a place you don't want to be, don't use it.

If you want to have more airflow on the windshield use the distribution controls (one for left, one for right, on the left and right of the HVAC control panel) You can store your favourite blend of windshield/midbody/footwell air flow.

You may want to refer to your owner's manual, as there are quite a few iDrive climate settings to work through.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue