2003 ML-320 noise in dash

I recently purchased a 2003 ML320 with 38000 miles. On any random day I can hear a ringing noise in the dash when I start the car in the morning,(It can last from 2 min to 25 minutes). I called the dealership and they will not do anything until the noise is constant. Has anyone else had this problem?

Sounds like the aspirator moter used to cool the front electrical box, common problem.

The next time you hear the noise do something...put your ear up next to the dome light assembley, if you hear the noise better its the tiny motor used to circulate air over the interior temp sensor. That motor usualy has such a high pitched sound it's hard to tell where the noise is comming from and could be your problem as well.