I have a 2008 Santa Fe Limited. Today I briefly turned the heat on since the outdoor temp was cool. Later in the day, I resumed the A/C AUTO setting at 72 for BOTH sides of upper vent outlets. I soon noticed that the driver's side blows warm air and the passenger side blows cold air as it should. No amount of adjusting the temp control either up or down had any effect on the driver's side except for constant warm air. Now I know the passenger side can be adjusted separately but both sides were set for the same temp. Never had this happen before. Always before, if I wanted warm air, the warm air would come through the floor outlets. What's causing warm air to come out the top driver's side vents when it should be cold? Could a diverter door be stuck?