I have a 1985 Ford Bronco 351 w 4bbl HO.
The AC was converted over to 134a and it blows cold as can be. Except when you accelerate and the rpms go over 3000 then it goes to defrost.
To me this suggest a vaccum leak but I did a smoke test and found nothing and I am perplexed.
Any suggestions as what to look for would be greatly appreciated.
Tim