2004 Passat Buzzing under passenger dash

[bardica]

Seems like some small motor having to do with heat/AC is constantly in action, generating an intermittent, yet constant buzzing noise (a bit like a buzz in a speaker but on and off like morse code). I had a mechanic look at it and he said that he might have to replace the entire electronic control panel for the heat/AC. Anyone familiar with this type of thing? If you are does the fix make sense? Thanks for any help/ideas you can offer.