Thanks to both of you. I've resisted getting a Mityvac because I've resisted getting into the guts of it enough to DIY anything on the vacuum system. I guess it's time to venture into it.

Elaboration: airflow is not out the defrost exclusively. As far as I know, all of the ACC settings pretty much do what they're supposed to, except that with the normal A/C setting (recirc off, any fan setting), airflow also comes out the defrost vents, in addition to the center and side vents, so I believe the diverter is not the problem. Since the defrost element fails in the open position, and since the system defaults to defrost in the event of vacuum loss anywhere in the ACC system, doesn't that point to either a bad defrost element or loss of vacuum?

How about the question of getting at the defrost actuator through the glove box opening? Are you saying that that is not how it's done, and that the dash would have to be pulled if the defrost turns out to be the problem?

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't