Since this seems to afflict a number of 126 owners, I thought I'd share my band-aid to the problem of cold drivers feet.
My symptoms were a lack of air to the drivers footwell under all circumstances, but all other functions of the ACC system working fine, including passenger footwell.
I "quick fixed" mine by removing the trim panel above the drivers feet: a few screws across the top edge, one at the bottom left and a plastic 90 degree turn fastner going to the center console by the drivers right foot.
The panel can be pulled down and a plastic hose that feeds the upper air outlets removed, swing the panel further down and then pull it out of the ducting in the center console.
You can now clearly see how it is that the upper level vents have air, but the feet don't. The carpeted panel conceals a two compartment plenum, the lower part of which feeds the feet and door outlets. With this panel out of the way it was immediately obvious that the door flap that allows air to come from the center console to this contraption was swinging in the breeze, presumably it had become disconnected from it's vacuum servo.
I chose to fix it in the open position by securing a plastic bottle cap to the base of the air distribution compartment in the console using hot melt glue, thus jamming the flap open. This means that air will flow to the drivers feet in all conditions, I will have to wait until next year to see how this works out with the A/C running. Seattle has modest summer temperatures, so I don't anticipate too much of an issue.
Reinstallation of the panel is "vice versa", as the Germans would say. Getting the right hand edge of the ductwork to hook up correctly to the center console was a challenge, as you also have to manipulate a trim panel that goes around the steering column into place. It took me a good 15 minutes of jiggling and jockeying to get it properly back into place, but for this it was a very easy job.
Note that this does not fix the problem, but it addresses the symptom
I did not have the energy to strip out the center console in order to get access to the vacuum servos, and at least now for the next 5 or 6 months I'll have warm feet.
Kevin