I own a 1991 420SEL. This is my first time on this forum and the third MB that I own (previous MB's: 1967 250SE and a 1984 300SD). Anyhow, my "new" 420 SEL has an annoying little buzzing sound coming from the fresh air intake duct for the Automatic Air Conditioner Cpntrol. This is the little grill on the overhead console (where the front dome/reading lamp is located). Thenoise is louder when the car is cold and the volume drops when the car's interior is warm. If I put my thumb over the intake grill, the noise goes away (or it is muffled). BTW, I had a similar problem with a noise computer fan. I suspect the problem is with the intake fan that pulls interior air into the A/C controls. Has anyone else had this problem? Is this a DIY project? I could just turn the radio up and then I wouldn't hear the noise. But this "little" problem, in an otherwise near flawless car is driving me nuts! thanks for your help!

You're not alone...
I've got the same problem on my 300SL. It feels stupid complaining about this little noise but I really agree with you. It's very annoying! Sorry to say that I haven't fixed it yet, but I will - eventually.

See my post. http://www.peachparts.com/shopforum/tech-help/15585-inner-temp-sensor.html

Emilo: Sometimes it is the smallest annoyances in life that can have the biggest impact. It reminds me of an old Donald Duck cartoon where he is kept awake by a little faucet drip. By the time the morning sun rose, the little drip sounded like cannon fire. Same thing with this little buzzing sound. Oh well, I'll just have to get a new stereo to drown out the noise....