yeah, you might be right, killer.
I checked my vac hoses, and all "appear"' to be connected and still pliable, and I can see the cale and arm for the blend door open, and can hear the flapping when I turn it to cool, but I suppose there's no wat actually see the door open and close w/o taking it apart, right?
Killer, did you feel both your heater hoses before you swapped the core? Were they both hot? Warm? 1 cold?
A heater core swap is like a 6 hour job, right?