Camry Air Con Fault

[aidan]

my 94 Camry estate blows very cold air from driver side vents, but tepid air from passenger vents. I have just had it re-gassed in last two days, so it is full of refrigerant. I have been told that it is possible that there is something called a "blend door" whcih may be stuck closed and not sending cold air to passenger side. I had a look around vents and footwells and there a number of little black boxes on the drivers side air ducting, any of which could be a small door motor.

Can any one help with this problem?

Thanks