Hmm, I didn't intend it that way, but yes, that fits perfectly!

While the conversions are less than optimum, there's no reason to stay with
R-12.  R-12 is expensive, and only going to get more so as supplies dry up.
Conversions from R-12 to R-134 aren't going to be that efficient.  But the
first thing I would wonder is if you convert, have it done right, not just
try
to fill the system with the wrong stuff after changing connectors.

Repairing an R-12 system will be expensive and only done by certified
'freon handlers'.  And R-12 systems are old, and going to continue to break
and need repaired.  And refilled.

With R-134 you can repair it yourself.  I put a new condenser on my Pontiac
when it ate a bird and eventually leaked.  Took it to the shop, and the guy
hooked up, evacuated for 30 minutes, then filled it for $50.  Try that with
R-12.  If I had an adapter to pull a vacuum,  I could have done it myself,
then filled it with cans of R-134 from Wal-Mart.

If the system is done right, there's no reason R-134 can't give performance
similar to an older system.  My 93 Intrepid came with R-134, and that was
the coldest A/C I've ever had in a car.

Just be aware that any repairs that require recharging will be way more
expensive with R-12 than with R134A (both because of the artifically
high price put on R-12 and the shops will charge more in general because
it is not the standard, so they have to give it special handling, and
they want to encourage you to abandon it or convert).  The downsides of
switching an R-12 system over are that the operating pressures are
higher, so the likelihood of a hose (which by definition already has
quite a bit of age on it - unless it's recently been replaced) rupturing
is greater.  As you point out, the R-12 system was not optimized for
R134A, so it will be less effective and less efficient.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

That isn't true of all cars.

R134 systems require a larger condensor.  Some cars have pretty small AC
condensors, just barely big enough for a R12 system.  And some cars have
adequately sized condensors but have poor airflow through them.

If the body is the same, you can get a larger condensor from a R134 system
in a newer model in a wrecking yard.

To properly switchover an R12 system you basically have to do this:

1) replace compressor (your never going to get all the old oil out)
2) Replace dryer
3) Replace all A/C hoses with barrier hose
4) Replace all o-rings with newer o-rings that are compatible with PAG oil
5) completely clean out the condensor/evaporator and all metal A/C lines
by running at least a quart of mineral spirits through them.   There is a
fairly
inexpensive flush gun on the market that does this.  You need an air
compressor for this.

I have done one of these conversions on a 1984 Chevy.  It worked OK.
The AC only didn't keep up when the car was idling in traffic.
Unfortunately the particular model chevy I did it on used the famous
GM DA-6 compressor and these compressors have a max lifetime of 6
years for a brand new one, 3 years for a rebuild.  Mine lasted 3 years after
the conversion then fragged.

Generally it's not worth doing the conversion unless your going to have
to replace the compressor because of it failing.  Since a proper compressor
replacement requires flushing the system, it's not that much more to do the
conversion.

Ted