96 air con control unit ?

[colsaudi]

Hi every body peeps..Can anyone put me straight on the whole pre 98 air con control unit issue? My 96 a4 air con unit is malfunctioning,can turn temp down but not up again,digits failing, and I can get my hands on a unit from a 99 model, but have been told that it might not be compatable is this right?,they look exactly the same, does it not function at all? or do some parts work? and is it just a case of swapping some terminations on the multiplugs at the rear? Information gratefully received..