The automatic controls utilize three temperature sensors to determine how the HVAC module controls the temperature inside the car. The ambient temperature sensor, sunload sensor on the dash, your vehicle may not have this, and you see the small "grill" in the auto unit? That feeds to another sensor under the dash. You would need to install the temp sensors, change the motors and replace the module along with rewiring and rewriting the system.
Your manual controls operate the various motor functions for temperature and fan by utilizing a potentiometer for temp and direct control of the fan motor.
Had the same question. Looks to be much more trouble than it's worth. Thanks y'all. Guess since I can't tinker w/the house right now, I'm spending too much time here looking for easy-kill upgrade projects for the Subie.
Personally I don't like the fancy controls. Tapping a button to cycle through the desired fan speeds is retarded. I much prefer manual controls. Although my tbird has a fan speed dial that doesn't have notches. So it's like a volume controls, you can make very slight adjustments to the fan speed. I love that. But in the tbird, you change the temperature by tapping buttons, so I guess nothing is perfect.
Turning manual knobs like on a 50 year old tv set is very y2k isn't it? Auto just hit auto, set to desired temp and that's it, no need for fan speed control, vent selection control, temp control, guess what its automatic.