My 1993 300E has this feature.

I really never use it, but I think if you turn the key to the left and hold it (in the drivers door), all four windows and sunroof will open.

Likewise, if you turn the key to the right and hold it, all the windows and sunroof will close.

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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".