5000 Turbo A/C questions

[ti@bazooka.amb.org (Ti Kan)]

Hi all,

If you are familiar with the inner workings of the 84+ Audi 5000
climate control system I'd appreciate your comments.

I finally got a chance to take a peek at my parent's 84 5000 Turbo.
They were complaining that the A/C doesn't cool.  Upon playing
with the system I discovered that the A/C will cool quite well
if I set the climate control's temperature to 60 deg F (max cool
setting), and the air comes out of the dash vents at high speed like
it should in this setting.  However, if I set the temp to even one
step higher, the system changes to only blow air out of the footwell
and dashtop (defrost) vents, and the blower fan decreases to a very
low speed.  This is with an ambient temperature around 90 deg F and...

The fact that it cools fine at the 60 deg F setting means that
the compressor and related components, as well as the refrigerant
charge are probably fine.  I thought perhaps the inside air temp
sensor is kaput, making the control head "think" that the interior
temp is cold?  So I looked through the Bentley manual and found that
there are two temp sensors wired in series: the inside air temp sensor
and the evaporator temp sensor.  Since the latter is under the plenum
and relatively easy to get to, I checked it according to the Bentley
and found it to be pretty close to spec (37.7 ohm, ambient around 80
degrees).

This leaves the inside air temp sensor as a potential culprit.
Before I dig into the dashboard to get this sucker out, can you
advise me if I am on the right track?  Any other things I should
check?

Many thanks in advance...

-Ti
94 A4 2.8 quattro
84 5000S 2.1 turbo
80 4000 2.0
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