Energy conscious heater

[JanDebL at aol.com]

The HVAC system on my 91 2c has developed a new quirk.  The heater works fine 
- until the temperature reaches the setting on the display and shuts itself 
off.  Then it won't come back on automatically.  Shutting the unit off for a 
while (not fun) will usually let the heat cycle restart, but not always.  The 
heater always work the first time.  Its also getting colder, -22 F Sunday.  
Thank the Audi gods for seat heaters.
Any BTDTs before put on my coveralls?
Jan Lahtonen