wouldn't the sensors basically tell the computer to move the motors and open the flaps? i have verified that when the tempter knob is adjusted the flaps move to adjust the amount of air that comes from the heater case. it seems more like there is just not hot air coming from the case.
the HVAC system is not exactly a simple system, but the more i read into it the more it sounds like a Heater core, and that there is a partial build-up/blockage stopping fluid from going into the cell that heats the driver side (US driver side). The blockage doesn't seem to impede the overall flow of fluid in and out of the core, just impedes it from flowing through that side. It's a bit different that what I'm used to seeing, but seems to be a reoccurring theme.