At 05:23 PM 4/8/2008, Jack R. wrote...
>GoWesty provided the most in-depth explanation I have seen so far.
>Nothing like the "simple" German engineering of a Vanagon!

But, they have it somewhat wrong. In describing the top lever, they say
it's for defrost, and only talk about it controlling the defrost vents.
At least on an '81, it's much more complex - it also controls the
front/center foot vents and the rear cabin floor vent. I think the
defrost vents are always on, but moving the lever toward the right
progressively shuts off the heater vents, so more air is then delivered
for defrost.