'86 944T, I have a copy of the manual.  

Problem: I'm being roasted out with hot air.  It acts like
the internal temp control is rotated to maximum heat all the
time.  With the fan off, I still get a very hot slow stream
of air into the interior.  To reduce the stifling heat, I've
pressed the recirculate air button and keep the fan off.
Occasionally, the temp will drop and things will work
correctly.  I don't hear any noises or lack of noise that
clues me into anything happening or not happening.

Page 87-27 of the manual shows a "control motor for
temperature mix flap and baffle flap." Page 87-28 shows a
"solenoid valve for heating valve" and a "vacuum line for
heating valve" I'm not sure of the difference between the
heating valve (vacuum)  and the control motor for the
"temperature mix flap and baffle flap."  Is that a single
flap or two different ones?

It's hard to tell from the picture, but is the control motor
an electrical motor driving a continuously variable position
flap to get mixing?  Any comments on how hard it is to get
to this?

The fresh/circulation flap is vacuum driven, and that works,
so it looks like the vacuum is OK, at least in that part of
the system. (I suppose there could be some leak that affects
only the heating part.)

Am I correct in suspecting that either the "temperature mix
flap and baffle flap" isn't moving or that my sensors aren't
sensing the correct temp?

If anyone has any suggestions, I'd appreciate them.

Thanks, in advance.