AC outlets
 

This pertains to 1988 300E...

My windshield vent arbitrarily will open and the center vent close for no apparent reason. This, of course, is summer and whenever the windscreen vent opens allowing cold air to blast on the inside of the windshield, condensation forms on the outside necessitating the use of the wipers to see !! Very annoying. There doesn't seem to be any pattern to this phenomenon. I am a retired mechanical engineer and things like this irritate the devil out of me when I can't ascertain the cause...just live with it ???

Any ideas ??

--Jerry