'85 5000S climate control - no heat

[Steve Barber <steveb@cme.nist.gov>]

Now that it's cooling off, my wife has discovered the Audi's
not putting out any heat.  (This just after having the A/C
compressor and R/D replaced.. possible connection?  The first day
I picked the car up after that, it was stuck on full hot 1/2 way
home until it finally unstuck.  Now I seem to have the inverse
problem.)

Other symptoms (note that we've only the car a few years so I
don't necessarily know how everything works when it's normal!)
include: only the dash and floor vents seem to work no matter
what the settings.  (Wife says occasionally the other vents
start to work, but I've never seen this.)  And I'm seeing strange
operation of the control head WRT fan speed.  If I start at off and
select ECON, sometimes the fan doesn't start.  Same is true for
anything else except defrost.  Selecting defrost always seems to
start the blower up full blast, at which point I can switch to any
other mode and the fan will continue to blow (possibly at a slower
speed).  Lastly, the fresh/recirc flaps don't seem to work right.
The flap at the passenger's feet is always open although I can see
it occasionally try to close maybe 1/4" or so when I change settings.
This flap appears to be connected to the outside air flap, which seems
stuck at about 1/2" open and I can't see it move at all ever.

I went back through archives about debugging these problems and got
a list of things to check for:

1. heater control valve appears to be working.  (changing temp
   setting moves the arm on the valve, and when set to hot, I'm
   feeling both heater core hoses get hot.  This also suggests
   to me that I don't have a plugged heater core.)

2. vacuum leaks: unplugged the vacuum connector from the programmer
   and checked all the lines.  Black pulls about 20-25 lbs of vacuum
   when the engine is on.  Of the other lines, blue leaks down
   pretty quickly (almost as fast as I can pump it up with the
   mityvac.)  Green, yellow, and red all seem to leak very slowly;
   I'd guess it's acceptable.  However, a couple of them do leak until
   you get enough vacuum on them to move the servos a bit, then they
   seem to hold okay.

   So I traced blue back to the servo behind the A/C control head,
   not seeing any obvious problems.  (Is the spot with a black covering
   on the hose a joint, or just protection?)  However, I notice that
   there's a second connection on that servo with nothing attached.
   I can't tell for sure if there ever was, and I don't see any loose
   hoses.  (I didn't have the dash apart, so I may have missed something.)
   The other servo more on the right side had the green and yellow lines
   attached; does there need to be a 2nd line on the blue servo?  (I tried
   plugging the port with my finger; blue still wouldn't hold a vacuum.)

So, anybody have any hints?  I presume I need to replace that vacuum servo,
but I don't see how this could be interfering with the heat.  Is there
anything I'm missing?  (I didn't pull the programmer off to test the valves
since I was more concerned about the heat than the vent control at this
point.)  I'm at a loss...

Suggestions about the other incidental problems would be appreciated as
well :-)

Thanks,
Steve