If you see some bubbles, you have a low charge, not none. Originally it had R12, might still. You'll want to check, if the fittings have been changed that is a quick tip-off that it has been dowgraded to R134a or ??, if fittings are original then might be original.

If it is still R12, have it charged not changed. R134a isn't much cheaper than the original R12 now, and R12 is much more efficient (read COLDER) with the original compressor if all works.

- Jeff Miller
'87 190DT
'85 4kQ
'88 Cabrolet
all w/ ice-cold R12 systems (Audi has used 1lb since new in '85)