More HVAC questions

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

So this is still on an A/C A1. I did the tests prescibed in the Bentley, as
follows: Add vaccuum guage into line shown, put heater control levers to
the right, run till guage indicates 15mmHg, turn off car. If it drops in
less than a minute, it's supposed to indicate a vaccuum leak, a bad check
valve or problems with the vacc booster, or other misc vacc servos and such
in the dash. So the guage reading dropped to zero immediately. 

I used the (unlit) propane torch to check for leaks and came up with
nothing, and it'd have to be pretty well a gaping hole for it to drop as
fast as it does. Idle's too smooth for a really bad vaccuum leak. So
assuming it won't be just the check valve (which I have a spare for now,
and will try tomorrow) how do I test those other servos and the booster?
Bentley leaves me lacking on this. It just says to test them.
This car <gasp> needs to have heat that isn't permanently on "defrost", and
I'd like to do it while the car is actually running AND the weather isn't
TOO cold. This is outdoor work so I don't asphixiate myself, so any tips
are, as always, appreciated. I'm really hoping it's just that check valve.
cathy