something very simple works for me,i try to keep out variables cus i'm a lazy git and can't bothered to think,so i keep to just 2 temps,20 when cold and 16.5 when hot.At 20,the thing can keep itself happy,whether i have it in auto or flick the snowflake off and use outside air to save fuel,it doesn't matter,the system copes.
But using 16.5 degs when its warmer outside,ie i need the aircon system to cool the air,then what works is to blast the car using the low setting,then turning to 16.5,leaving the fan to run at 3/4,then manually turning the fan to 1 after about 2/3 mins,then flicking the auto button back on.Hey presto,i dont need to touch it again!
doh! its supposed to be an automated system! it works though.