Defrost / air issues

I have a 95 ford explorer, when i turn the defrost on the engine shuts off, when i have the air on for more than 45 minutes the air turns off like it was never on but the car still runs please help

Sounds like a vacuum fault, but where?

A better description surely would help. E.g. when you say 45 minutes with the “air on” do you just mean the blower motor going, or do you mean with the A/C running? Does the A/C work? Did these two problems start appearing at about the same time? Or has one been around longer then the other? I.e. should one assume that both things come from the same problem? (b/c they very well may not) When the engine “shuts off” does it die completely and suddenly? Or does it sort of choke and spit and sputter, and then die? You description doesn’t give anyone much to work with.