Looks like my Gremlin is back. Had this issue a few years ago and it went away.
The issue: driving the car on a hot day with the HVAC set to auto at 69° and the AC blows nice cold air. Then at any random time the center vents start blowing HOT air. This will continue until you stop the car and turn off the ignition for 5 or 10 minutes. This includes; getting gas, grabbing food, stopping at the store. After that, you start the car and everything is back to normal until the Gremlin comes back.
The quick cure, I found for it on the way home from the Mafia Family Reunion is, to press the manual buttons for Floor and Vent at the same time. Once these are set with the green light illuminated, I get cold air. This isn't as good as the Ice Cold Auto mode but, cold enough to be comfortable.
Any Ideas?