I recently bought 2002 ML 500. Once I start driving the windshield gets fogged outside ( it is humid). In some 5 min I have to start wipers otherwise I cant see much. Looks like it happens because of AC ( on AUTO) blowing from the top air outlet. When I turn the direction control to sides only it keeps air coming from the top. I was trying to change controls for volume and direction and at some point it switched to blowing only through sides and it was OK till the end of the trip. Unfortunately do not remember what I exactly did I do. The only thing helps is start defroster but then when it switched to AC it eventually get fogged.

 

just set the air distribution switch to center and side or just center. never to the defroster vent. try manual and not auto.

 

I did try air distribution switch to center or sides but no matter where the switch is it's still blowing from the defroster vent.
I am trying on manual AC not AUTO. On AUTO it alwas blows defroster.

 

My neighbort had the same problem, on a 2004 ML she bought, finally after many trips to the dealer they replaced the windshield, something to do with the laminate. That is all she remembers about what they said caused the problem. this is the second windshielf, the original was broken at the dealer, replaced and the OEM replacement had the problems the original was OK by the way.

 

Do you drive with the windows open?

 

Windows always closed. Actually I just bought the this '02 ML500. So far I had only 5 trips.

 

sounds like the sun sensor is faulty.

take it back to the dealer for free check.