[CQ] R-134a A/C conversion?

[Bob.Sandy@USPTO.GOV]

Has anyone ever attempted (and/or succeeded) converting their/an Audi
from R-12 to R134a?

The A/C in my 1991 Coupe Quattro just quit.  The climate control[ler]
seems to check out o.k. according to the fault diagnosis described in
the Bentley.  However, the compressor does not turn on.  I suspect the
system pressure is too low to turn the compressor on.  

Before I consider having the present R-12 system corrected, I thought
I'd ask if there has been any experience(s) and advise from the listers?

Thanks,
Bob