If you have the center button depressed, even with the knob to full heat, the a/c is always running, even though you are not aware of it.

MB designed it this way to remove humidity from the air.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".