The car has thumbwheel temp control like all other US cars.
I sepnt a few hours this morning trying to replicated the problems I have.
1) Swithching from heater to A/C: This morning, outside temperature was close to the freezing point. Started the car and a few minutes later, the heaters starts blowing hot air. Normal. Inside temperature gets to the setting temp (about 68deg). No hot air is comming out of the center vents (also normal). All of this was done at fast idle (1,500-1600RPM). I let the car return to normal idle (700RPM) and about 30 seconds later, the heater turns to cold (A/C) with cold air coming out of all air outlets (dash/floor). A little tap on the gas pedal and the heater turns back on. (nothing's blowing out of the center air vents).
Then I put an air dryer directly in the temp. sensor (near the rear view mirror). A/C turns on nice and cool as long as the car is running at fast idle. If I let it run at idle speed, the heater's on. Again, a little tap on the gas pedal and I'm back at full A/C (normal). I'm totally lost