Jonny5oh

Hi all,
I've got a 2010 S4 and my A/C doesn't function at all. I know there are a lot of threads about the G395 pressure switch and also a broken LIN wire. but I don't know where my issue fits in so I'll post a brake down of whats happening. I bought the car a week ago and the A/C worked fine on the drive home. A few days later I pressed the a/c button and the light comes on but there is no cold air at all. When I turn on the a/c on my other cars, you can hear some flaps move, there is a bit of a smell when it first comes on there is a momentary dip in RPMs etc. There is absolutely no reaction to pressing the button at all. The next day, I tried the A/C and it functioned normally (heard the flaps move, air got cold etc) and it hasn't worked again since.
I scanned the car with my OBD11 scanner but it shows nothing and I ordered a ross tech cable this morning so maybe that will dig up some more info.

So here are some questions.
Does this sound like the symptoms of a bad ac pressure switch or broken wire? I noticed most people state that their ac button would not stay on but mine does.

If it is the pressure switch, does replacing it require draining the refrigerant out of the system?

If there were fault codes in the AC control module, would they not show up on a generic OBD scanner?

Thanks for reading...any input would be greatly appreciated!