Sounds like the actuator that works the blending door is screwed up.
The blend door actuators are reversible, 12-volt direct current (DC),
servo motors. Models with the single zone heating-A/C system have a
single blend-air door, which is controlled by a single blend door
actuator. Models with the dual zone system have two blend-air doors,
which are controlled by two blend door actuators.
The blend door actuator for the single zone heating-A/C system is
located near the center of the HVAC housing , close to the instrument
For the dual zone heating-A/C system, the same blend door actuator used
for the single zone system becomes the driver side blend door actuator,
which is mechanically connected to only the driver side blend-air door. A
second separate blend door actuator located at the front of the
HVAC housing is mechanically connected to the passenger side blend-air
All actuators are interchangeable with each other. Each actuator is
contained within an identical black molded plastic housing with an
integral wire connector receptacle . Each actuator also has an
identical output shaft with splines that connect it to the
respective door linkage and three integral mounting tabs that allow
the actuator to be secured to the HVAC housing. The blend door actuators
do not require mechanical indexing to the blend-air doors, as they are
electronically calibrated by the A/C-heater control.