New '06 MCS owner here. Whenver I turn the auto a/c on or off, I get a brief electric whirring sound from the glovebox region. Like a motor spooling up. It goes away and doesn't return unless I shut the climate control on or off again. I reckon this is normal, but I wanted to make sure.

Anybody know about this noise?

 

That is normal, it's the sound of the mechanism used to route the air to the various outlets as well as control the temp and select recirculated vs outside air intake. On turning the system off, the system will usually position the air control doors to a certain 'default' position. The whirring sound is the little motors doing their thing. It's completely normal, and also louder in some cars than others for some reason.

 

Many thanks! A 1.5 hour drive to the dealership with only 3,000 miles was not so appealing!!