01 Grand Caravan Heater fighting AC

With the AC on, the dual-AC rear zone blows cold, while in the front, hot heated air is blowing from the center and driver's side vents. On the front passenger side the hot air is mixing with the cold air to produce only luke-warm air.

I tried following instructions from past posts on how to recalibrate the AC/Heater control unit, but they seem to apply to older models and didn't work for my '01.

My owner's manual described changing some ventilation control system options by first holding down the power button before starting the van and then push other buttons after the power button starts flashing, but the book didn't cover re-calibrating the system. Does anyone know the correct procedure for this model year? How can I test if a failed blend door actuator is my problem?