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It sounds to me like the flap may be stuck, rather than the control head. You can get to the backside of the control head and disconnect the cables to check this. it's possible that something on top of the dash may have fallen down the vents and be catching on the flap. I have had to remove the airbox on one of these due to a child sticking stuff into the vents and it causing flaps to stick. it involves removing the entire dash to access it.
Luckily you are on the West coast! I know in the Seattle area there are a couple places to check. Absolute German is a wrecking yard south of the city, and the Campbell-Nelson dealership also owns a yard about an hour north of Seattle. I'll look up their contact numbers a little later.
Great! I know Busdepot does a lot of work with the older stuff, but a lot of those companies are starting to catch up with the Eurovan since it has become an orphan- GoWesty is also another place that deals mostly with Westfalia and the Vanagon, but may have something for you if you ever need it.
If you're ever looking for just stock parts, you can also check with Europarts-SD dot com, and if you call them Steve Schock will always remember you and your vehicle!