iF YOU select "0" then no air should enter the interior. IF air still comes in, then the fresh air vacuum element isn't closing the fresh air door.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
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44 years foreign automotive repair
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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