It's sometimes hard to believe that the Vanagon originated in a country where
it has snowed sometime during the past century.  Here's a thought for those
who are freezing their chalubies in the winter until the rear heater starts
cooking.  If you want a front heater which relies on totally recirculating air,
blank off the fresh air intake to the heater box and remove or prop open the
gravity dampers in the heater box.  The fresh air intake can be blanked off at
its opening behind the radiator grille or, if you do not mind pulling the
heater box, the fresh air opening in the heater box itself can be sealed off.  In
the earlier vans, the make up air will flow through opened dash vents and cabin
fresh air vents (as long as the cabin air damper in the heater box is in the
opened position) and in the later vans the make up air will flow through the
cabin vents alone.  Perhaps the outlet air vents at the trailing edge of the
rear side windows would also have to be blanked off.

Or, if you're really cold and into that rat rod look, just blank off the
fresh air intake, plumb in a spare rear heater box parked between the front seats.

George