So I've got my '86 Westy, and it's AC system is not working.  Over
the years I've tried the $30 switch to R134a and replaced the leaking
expansion valve, and got a little cool out of it, but not enough to
keep the van cool while driving.  I really need to replace the
receiver/dryer and figure out where it continues to leak slowly.

But I'd also like to have AC when I visit a campground in the
summer.  I've seen the rigs to mount the window AC unit in the
passenger window or in the luggage rack.  They seem to require more
setup/take down time than I'd ideally like.  I do like the fact that
you just leave the whole thing at home in the cooler months.

So here's my idea.  Use one of those freestanding rolling AC units
that has air exchange hoses to connect to a window.  Strap it in
place somewhere like behind the passenger seat.  hook hoses to handy
window with DIY adapter plate.  While camping it uses shore power--
easy.  For driving it runs off an inverter connected to aux
battery.  Here's my concept breakthrough: replace the AC compressor
on the engine with another alternator.  They're cheap, even for an 80
or 100 amp model.  100 amps = 1200 watts.  Should be pretty easy to
fabricate a bracket to mount the additional alternator.  It will not
put much load on the engine when there is no load on it, or it's belt
could be removed in the off season.

Questions/Ideas:  Is 1200 watts enough to power an AC unit big enough
to cool a vanagon going down the road on a hot day?  Or one parked in
the sun with the top up?  I'm thinking some adjustable air deflectors
inside the van to direct the cool air toward the drivers when driving
or elsewhere when not.  Maybe big flexible hose for that?  Perhaps
the outside air heat exchanger could take advantage of ram air when
moving to improve efficiency?

Edward  (also added another vanagon post on my blog
http://gismemories.blogspot.com )