AC blows hot air. compressor good , lines get cold to firewall but only blows h

What is your question?

Comp. works good and lines get cold to firewall but only hot air comes out. and on the floor position no air comes out on heat.. This is A 1991 Lincoln Town car. the air door works ok. the blower works great. It is like the air from the blower does not get directed through the AC core to cool it. I am looking for a way to correct the problem without taking the whole dash apart and out. I am a retired mechanic but have never worked on AC.'s

What makes this problem better or worse?

worse when engine gets to operating temp.

How long has your 1991 Lincoln Town Car had this problem?

few weeks