Air out of dash but not vents??

[87gninpa]

I get air out of my dash and floor, but not the vents. I thoguth they were controlled somehow by vacuum, is this true?? my 88 IROC has this problem also. anyone know how to go about correcting this??

 

[fitz3820]

Yup, vacuum controlled - behind the HVAC controls on the dash.

There is a vacuum manifold that spins as you move the hvac lever.
They usually develop a leak after a while.

I got a new one at my friendly neighborhood GM dealer for $15 or so. Sorry - I don't have the part number.

 

[87gninpa]

thannks fitz, anyone happen to have the part number? how will i go about installing it??

 

[BlackBeauty]

Check all the vacuum lines in the a/c system. One could be unplugged or clogged.

 

[wagon]

I have a used one here in an AC Delco box, and it says 'valve vac', so I am guessing it is the right box.
This looks like the part number1#15-71389, or maybe 1#16037778, they are both on the flap. The bar code on the side has this: 0 36666 30717 7. One of these is bound to be right, I would guess. Also, there is a 3 port check valve somewhere off the back of the intake manifold. Check to make sure this isn't popped. If it is, then you probably have a popped bladder on the doohickey that opens and closes one of your vents. Good Luck, let us know what you find.

Brian

 

[justabuickv6]

If you have been running high boost, one of the vacuum lines going to the EGR may have come loose. This happened to mine before but it's now zipped tied.

Other than that, it may be the part mentioned above. It's behind the HVAC controls. Small circular black vacuum device that has about 7 or so lines going to it. Part was about $10 at the dealer.

 

[87gninpa]

Thanks for al the opinions guys, i did the intake man gasket about a month ago and replaced all of the vacuum lines so im sure its not that because it was doing it before that. ill try those part numbers at the dealer and see if that works
thanks again