on the jeep---2001 Grand Cherokee--with noises coming from the dash---passenger side. I HAD SOME EXPERTS LOOK AT IT AND IT IS THE "BLEND DOORS". The vacuum and/or the motors go bad. Some are accessible. Others require the removal of the dash--(approx. $1500.00 in labor) CARMAX here I come!
This makes me remember my 1951 Dodge--that had a big handle under the center of the dash---push it down to open the vents and let in some air. That coupe cost me $40.00 at a NYC Police auction.