w210 air wont go out of recurculation mode

[nickh]

my w21 e class 1998 with climate control, seems to have a small problem that if i use the air recurculation mode, it wont open back up to let fresh air back in.. I removed all ther plastic panels in the engine bay to see the fresh air flap, also removed pollen filters, etc.. I can see that if the flap is open when I press recurculate button it closes, fine, but when i press to stop recurculation it stays closed?? This seems to leed to very bad misting / steaming up.. although sometimes even with the aircon on it does not clear (i have looked at other threads on this.)

Does anyone know if this indicates a problem with the aircon or something mechanical or even some computer reset needed??