Hi all...This list is great!  My first post:

I've got an 85 Westy, purchased about 4 months ago.   When first
purchased, the AC worked poorly.  After being in the shop and not
getting much driving, I recently discovered the AC didn't work at
all.  It sounds like the compressor engages, but when I tested the
valves there was no R12 pressure at all.

So my theory is that there is a slow leak (6 months or so to fully discharge).

So, any advice on the pros & cons refilling with R12 or converting to
R134?  My theory is that if there is a slow leak, I'd rather be
leaking R134 than R12.  Cost is definitely an issue, so the $40
do-it-yourself R134 conversion is attractive (assuming that having a
mechanic fix the leak and refil with R12 would cost hundreds of
dollars).