AC question 1996 A4 2.8L

[gavric]

My friend has 1996 A4 2.8 and his AC was starting to blow not soo cold air. So he did quick refill with one bottle of 134A from parts store. Thing is that he went to great trouble to find adapter to fit that refill hose to his AC piping. After he has put that bottle in his AC died all the way.

Now someone has told us that old R12 systems use weird adapters and that if you put wrong coolant thing inside AC system you will mess it up. Anyways his AC is not working now at all.

Question to you guys is which system his car (1996 A4 2.8)uses because he doesn't has any stickers or anything under the hood to say what it is and also where he needs to connect the hose to refill it again. He does it behind left headlight.

Thanks