My friend just called me needing a fellow VW owners shoulder to cry on.
His 93 euro just caught on fire on the highway when he attempted to turn
the a/c on.
This is his fourth and only problem he has ever had with the van. All
air conditioning related. Two locked up compressors causing the
serpentine belt to snap and other relay and electrical problems.
Yesterday his attempt to turn his a/c on going 60 mph on rt.  55 caused
a major electrical fire with flames included.
Aboard his vessel like all of us (correct? ;) was a fire extinguisher to
save the van. At this point he regrets not letting it burn to the
ground, but he'll get over that.
I'm still not sold on 134a. He is one of three people I know of with a
track record of grief connected with it.
When the stuff first was introduced I had a class on it, the description
of 134a that was given is, the chemical composition suspends everything
in it. That means the junk from normal ware and tear settling down in
the oil out of the  refrigerant flow, like with R-12, continues to
circulate thus causing more/faster breakdown.
One of the main reasons the proper filter/drier is a must with 134a.
I don't want to sound old school, but if your system is tight and in
good working order, stay with r-12 or a direct replacement for it. Those
with 134 already all I can suggest is check into the latest filters for
any improvements, and possibly add redundant fuses for the compressor.
My 2 cents.

Rob