Air only thru dash vents
My 2003 F150 KR is doing something similar... I select FLOOR and all the air is directed to the defroster! When I select VENT, all the air is directed thru the dash vents. Same with FLOOR+PANEL. No air goes to the floor. Right about that time, the driver's seat "bun warmer" quit. the indicator lamp lights, but no bun warming. I wonder if it's related. Getting at the HVAC module is brutal.