Cadillac: interier heating, radiater, vacuum system

Question
When it is cold outside.. The heater blows cold air..  The levels in the radiater are topped off..  It blows cold air after the engine is warmed up.. After I shut off the engine for a few mins..  And restart the engine..  It starts to blow hot air..  What could be wrong with it?

Its a 1991 Sedan Deville.

Thank You for a answer..  If you have one.. Need Help on this  

Answer
Obviously you have an intermittent fault either in the vacuum system and or the AC-Heater programmer or in the damper door.

With the engine running try moving the controls from extreme AC to extreme heat back and forth to see if any other symptoms develop. Having access to the vehicle the fault is no problem to find, Trying to tell you where it is without doing numerous testing is most impossible.

See if you can get me more symptoms.

tom