Here's my solution to the problem. (With thanks to another forum member who came up with a similar solution to a similar problem)

It's a quick fix until I get another reason to remove the dash and replace the actuator. Since the leak was only occuring when the actuator was in the completely closed position and worked fine once the actuating rod was pushed in a quarter inch or so, I took a piece of approx one eighth inch thick flat aluminum stock about six inches long. I bent a 2 inch section of it back on itself into a U kind of shape. I removed the rubber boot on the vent and put this down into the center vent ducts while the flap was open so it is hooked over the edge of the ductwork. When the flap closes, it can't close all the way due to the aluminum stock in the ducting so that now the actuator works just fine. Of course, the flap does not close completely but it is very close to being shut off and if I want to completely shut it off I can use the manual shut offs at the dash vents.

The fix is neither perfect, beautiful or elegant but it is functional and almost certainly the equivalent of the engineering that necessitates the removal of the dash to replace a vacuum actuator.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13