Vintage Air Gen IV Problem- Blows Cold, Then Warm

[67ChevyRedneck]

I have an old sure fit system in my C10 that's been blowing Ice Cold since 2006.

I installed a new Gen IV sure fit system in my 65 Mustang with the electronic controls that's having issues. I have emailed V/A but haven't gotten a response, I will call them after I mess with it more this weekend.

Thought I would ask all the experts here to get some more input before I call them.

What's happening:

When the car is first started, the A/C runs/blows cold as it should. After 15 to 20 minutes of operation the compressor no longer cycles on and it blows warm air. The system was installed over a year ago and worked excellent until a couple weeks ago (but A/C has not been "run" since about October of Last year.) They system was evacuated by a shop for a full hour and held vacuum and they filled it for me.

If you turn the dial to "heat" for a minute or two, or turn it off for a few minutes, it will be cold again when you switch back to cold, or turn it back on.

Another weird issue... I never drilled a hole for the drain line. I've been using an old antifreeze jug with the hose going to it... when it's hot out, that thing would just about fill up with a few hours of use. I went to empty it and it was bone dry. I blew air up into the hose and everything sounds "loose/free" so it shouldn't be "plugged."

When it's not working I don't see any visible ice on any lines, there doesn't appear to be any oil at any fittings (no leaks?)