1997 Chevrolet Silverado • 165,000 miles

1997 Chevrolet Silverado K1500 4x4, 5.7 Liter V-8

The control **** which selects if air blows out the defrost, front, foot, or etc vents operates perfectly and the blower motor does also. When moving the control **** from foot to defrost (as one example) you hear a air whistling sound and then I hear a door flap open abruptly then the air blows out the correct vent.

What is the mechanism called that controls which vent the air flows to?
Is this is likely what I need to replace?

August 8, 2011.

Vacuum master select switch

Aug 8, 2011.
I appreciate the help as I have always had good luck with replies on this website.

Just to be sure, since I will be buying this part and then replacing it with help of my Chilton repair book.

The "Vacuum Master Selector Switch" is what I need to buy /ask for at the parts counter, and this should allow whatever door is sticking in the vents to operate correctly and direct airflow? I wonder because my switch at the instrument control panel works perfectly (just double checking I am buying the correct part for the problem described in my previous post)

Please confirm this is the only part I need to buy and provide a beginning idea of where this part is installed in my truck.

Thank you very much !

Aug 9, 2011.
Not seeing truck can't say if switch is fix. You asked what part was what you decribed is common to switch. Also called Mode select switch need to remove control panel

Aug 10, 2011.