Park Avenue heater/AC problem

The problem I'm having is cold air out of the driver's side center vent when set to mid-range temperature, e.g. 75F. If I run the set
temperature way up, e.g., 85F, it will route all air to the floor, and it's warm. I've confirmed vacuum to the system, and the coolant hoses to and from the heater are warm.
I have been searching old newsgroup postings and gotten several leads, but so far nothing has worked. One or two people have suggested an error display sequence i.e., simultaneously pressing Off and Warmer buttons to get codes to show up on the display. However, this doesn't work on my car.
Also, someone said to momentarily disconnect the battery in order to cause the AC programmer to reset. No help.
Any other ideas?
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