mine does exactly the same,no matter what i do,it never seems to clear fully.i have noticed that it seems a little greasy when i try and wipe it off so i used some strong gass cleaner and this worked fine for a couple of days but it has come back again and seems to be worse.even in the summer after i had turned the engine off there seemed to be a couple of small patches of condensation on the windscreen but i just put this down to the aircon winding down and expellinga little condensation.