My guess is not that the pump itself has seized, but rather the pulley bearing.

Mercedes sells a rebuild kit for the pulley and bearing in the low $200 range.

You can buy it at the dealer.

You remove the air pump from the car, install the new pulley and bearing, and re-install.

__________________
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".