Hmmm BA ghia blows cold passengers side only, figured the ole broken rod so pulled seats, column, dash etc and rods are fine, so are he doors in the heater unit. Friendly Ford chap suggested the HIM would have a dodgy mototr so opened the HIM, tested the motors (12v) and they are all good, so took the HIM to local wreckers, plugged it into a Fairlane ghia, powered it up and the HIM responded to all inputs from the ICC controls.... this ruled out the HIM as the problem.
Rang Ford again and service manager mentioned one of the guys (who was away that day) has a way of resetting the units which annoyed me no end considering had I known this I'd have done that first rather than pulling the dash etc. Soooo went back home and reinstalled everything back into the Ghia and reconnected the battery (disconnected to take dash out, didn't want an airbag going of or anything silly whilst mucking about with it) fired her up and what do you know, the bloody thing works again!
Well, that all went well until trying it again after fitting seats, A and B pillar covers, door rubbers etc and stuff me if the battery is now too flat to start the car (interior lights been on while refitting seats etc) soooo jump start the car, take for decent drive to charge batt and get the motor warm and..... it's blowing cold on passengers side again!!! Figured I'd try the disconnect battery trick and left it like that overnight, hooked it back up next morning and it's all good again...FFS!!
So, in summary, I would suggest the battery can indeed have an effect on the dualzone and trying that option first is wayyyy easier than pulling the dash etc only to find it aint the rod or door hinges.
Regards, someone who's done it.