Vanagon ACs is the 2nd biggest topic (after tires)....

There are some that state that it is inefficient. A properly working
(late model...aka 86 and later) Vanagon will cool the interior of
your Vanagon. Even with a dark colored vanagon without tinting on the
window.

On my 1986 passenger Vanagon, the AC (R12) when I got it was so
efficient, I could never use it at full speed (not without a coat
on). When I bought it (in Southern California) I travelled across the
country to Washington DC, via Phoenix, Houston, New Orleans, Tampa,
and then up the east coast. Outside of the Mojave and Death Valley, I
don't think you'll find too many other areas in the US with higher
temps.

Throughout this trip the only problem I had was that the drip lines
in the back weren't draining the condensation fast enough, and a
sudden stop got me a VERY cold shower.

My 91 Westy's was not functioning when I got it. It simply needed a
recharge, and then worked great.

If the vanagon's AC is converted to R134, there are several changes
that need to be made. Not the least of which is flushing the old oil
out of the system But also, more importantly for cooling, is to
change the evaporator nozzle(?) to accomodate the different
refrigerant. Pulling the evaporator on a Vanagon is not a trivial
task, so this little step is rarely performed in a conversion.

Hydrocarbon refrigerants (I use Duracool) can give the same cooling
capacity as R12, in a system that has already been converted to R134
(necessary for legality). All my Vanagons now use Duracool.

If your Vanagon's AC doesn't cool properly, then it needs work.

Westy's, due to their nature have different problems. Many folks
expect a car AC system to blow cool air in their face. Even if the
ambient temperature is much higher than comfortable, this method
gives the appearence of a "colder" AC system. The Westy, instead,
cools the ambient air (because there is no ductwork to allow it to
blow on your face.) This may take a few minutes to drop the interior
down from 100+ degrees (in the summer, my interior might be 130 F or
more, if it has been sitting in the sun.) The Vanagon's windows also
mean that you'll get lots of sunlight on your legs (contributing to a
feeling of heat, even when the interior temperature is down in the
70's.)

I don't have any experience with pre 86 Vanagon AC units (Behr, or
overhead dealer style). Because they blow in your face, you'll likely
"feel" cooler (your rear seat passengers won't though.)

So why isn't YOUR AC working? Most common issue is likely a leak in
the refrigerant lines, evaporator or condensor. The lines are longer
than in most vehicles. But you may have other issues. For instance,
is the thermometer setting working on yours? I've had to replace it
on one of my vanagons. This is the "switch" that turns on the AC, but
also sets it's cooling temperature. It is essentially a variable ohm
resistor. if it isn't working, the AC system may thing it doesn't
have to engage your clutch on the compressor (and hence no cooling.)
It's a simple thing to check (and simple to replace if yours is bad.)