RE: AC blowing out defrost vents..
Check for a loose vacuum line/cluster plugunder the dash on the passenger side. Sometimes a passenger foot gets under there and catched the vacuum cluster. Also check the black vacuum line that goes to the vacuum canister between the inner and outer fenders. The line will sometimes get chaffed thru by vibration where ot passes thru the inner fender.
"Have a good day, and a better one tomorrow"