Another one from East TN with an issue

[walnuts4x4]

OK. I tried the self test, no codes. The original issue was it quit blowing out the vents. It would blow out at defrost, just not out the vents. I was told by somebody, don't remember who, that it could possibly be a vacuum leak. How do I test that?

do a search i know this has been discussed but I would start looking around the firewall for a leak... may be a valve is also on the firewall somewhere may be bad... I know it has been discussed I just cant remember where it is