79 heritage ac not blowing out vents

[Aarontbird]

Hey just wondering if someone could help me with my ac issue it a 79 heritage with a 351w. It doesn’t seem to switch right. It doesn’t blow out the vents and the air doesn’t seem that cold. Ac system has been test so I know that is not the issue. I was told it may not be switching right in the dash. Just wondering if it would be a big job to do this, or if there is any other things it could be thanks

[voltron]

I had a 79 Tbird that had a leak on the vacuum canister. When the system fails due to a vacuum leak the dash panel vents default to the defrosters and I pretty sure it went in to heat mode also, it has been many years ago. The canister rusted at the crimps on the ends of it.