When the outside air intake is covered with snow or ice it will not allow outside air into the HVAC system. This causes the front window defroster to not be able to blow air on the windshield to clear the windshield. This is a very dangerous design flaw on behalf of Mercedes Benz. If hot water is poured over the outside air intake screen the blower will operate properly, blowing hot air to defrost the front windshield. Only happens if the car is outside with snow or ice buildup to block airflow into the HVAC system. Defroster will work properly if no snow or ice is covering the area.

- Interlochen, MI, USA