confusion about aircon
 

I have a 1994 Euro C180 and before it went to the workshop, the aircon was not very cold and ran like the usual Japanese aircon, just blowing continuously. However when it came back from there, after some vacuum work was done on it with parts replaced, the system is now blowing first in the centre vents, then the 2 side vents and going back and forth consistently. I reckon this is might be a design for good air circulation or allowing airflow to every part of the front. However, can I stop this back and forth recirculation whenever I want it to happen? Its very annoying and distracting for the driver although all passengers are fast asleep in no time! My question is whether this is the correct way for it to function or is there some fault in the controls, vacuum system or leaks? Now its very cold too.

When the A/C mode is selected the center vents should stay on!
If durning acceleration they go closed you must have a vacuum leak or vacuum supply problem.