Aircon Blend control problem

[arrkwill]

I have a Ford Fairmont 4.0L (2000 model) which could only deliver unheated air. Did the obvious - checked the hot water valve, and flushed the dash heat exchanger. No improvement. Bought the manual and (very courageously!) removed the dash - yes the whole thing! First for a 'dash virgin' - some exercise! My findings thus. The aircon module has 6 vacuum solenoid valves. One feeds the hot water valve in the engine bay, one opens the recirc flap, and the other four drive the air direction around the car's interior. All worked fine (you can suck on the pipes to check!) However the blend control flap is driven by an electric servo unit. I stripped and checked the servo-motor, and feedback potentiometer. All fine. I checked the wiring back to the climate control - all fine. Lastly I checked out the innards of the climate controller and found there are no control signals emanating from the microcontroller (which looks like a proprietary Motorola part). The (high current) motor-drive chip seems OK. All other aircon functions are perfect - cooling temp, fan speed, air directing, etc. so the microcontroller seems otherwise fine. So my question is this - what if some other input signal is missing causing the micro to never send control signals to the blend circuit. How can I check? Any suggestions? Must I replace the whole unit? Who makes these things (somewhere in Aussie I suspect).