I just got my 2006 C Class back today and FINALLY the dealer fixed the chirp in my dash. It was driving my nuts as when I would go to the dealer the damn bird would shut up...finally today I drove it in while the chirp was active. There is now a service bulletin related to the chirp noise...the fix is they install a piece of velcrose on one of the vent housing plastic parts that causes the noise. Tell the dealer about the service bulletin. My dealer is Germain in Columbus, Ohio and have them talk to Dennis in service...he showed me the fix.