The climate control air delivery is stuck on "BiLevel" on 1999 Buick Century

2 year old rebuilt A/C pumps 55 degree C air. Fan works properly. Rear window defroster works. Air is warmed when temperature control knob is rotated to "Warm" and mode selector switch is rotated to any position other than "Normal" or "Max". There is no indication that air directional door is operating.

Asked by for the 1999 Buick Century
Have the system tested, they got about 3 different types for this car!! We can only guess and be wrong every-time!