I'm having similar symptoms as the original poster.
AC seemed to suddenly quit working from one day to the next, based upon what my wife has described to me (I rarely drive the Passat).
1) I pulled the 384 relay, and a quick visual didn't show any obvious signs of problems. May need to pull it again and check with a magnifying glass (middle-age eyesight sucks).
2) Check for operation of the passenger-side electric fan, and it comes on with the AC on.
3) Checked the AC fuse (fuse #25 if I recall correctly) and that fuse is fine.
4) Inside temperature display is operational
Any other diagnostics I should perform before I either decide to buy a replacement relay and easter-egg it to see if it does the trick, or before I go to an AC specialist to have the whole system checked? I don't believe we've ever had the freon recharged, but the sudden change would lead me to believe that it's not the freon unless there was a catastrophic failure.
If the compressor turns out bad, it looks like I should have the following replaced:
- the compressor (Sanden or Denso) (is a Sanden-Behr compressor the same brand?)
- the drier
- is there an orifice tube to replace?
- is there an expansion valve to replace?
thanks,
Herb