It depends on which vents you speak of: the two vents that are parallel to
the facia and have open/close switches are fresh air only. The consensus is
that is that the two dash vents at the front are a mixture of fresh and hot
air. Hot air can be increased to these two by as you described, shutting
off the fresh air flow (2nd from  bottom); the two smaller vents that feed
the side windows are hot air only but the flow is fairly weak unless you
are moving or revving. As for increasing heat flow I have placed in the
line of the hot air flow (pipe is accessible at the front by removing front
grille) a 12 volt marine fan which provides enough hot air through all
four windshield defrosters for decent warming. This works even at temps at
or below 0 C. Earlier vanagons had no fresh air blower ; so yours may be a
transition model.....There was big discussion on this about 2 months ago;
check the gopher and search using the terms heat, vent etc.....Good luck - DC

PS blocking off the fresh air intake is also recommended....DC
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David Carment
School of International Affairs
Carleton University
Ottawa, Ontario
K1S 5B6
voice - (613) 788-2600-6662
fax - (613) 788-2889
Email address: dcarment@ccs.carleton.ca
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