If it seems to be working fine.... and you can find a good shop.... you might consider just having them replace the seal in the compressor , flush the system, and then replace the R12 ( which you should buy yourself off Ebay after getting your online open book test 609 license ).
This might be a low cost solution which will serve you for a long time...
You might not be happy with the 15-20 percent drop in performance inherent in the R134a compared to the R12... later autos designed for the R134 don't have that problem because they compensated for the shortfall in hard parts changes.

Thanks, Leathermang

I will check that out and see if I can get it done. Sounds like a better solution to me!

George

Ditto on the above. These systems SUCK with R134. When it gets really hot out, they just can't keep up. They weren't designed for 134 and can't use it effectively.

The two seals at the back of the compressor should also be replaced (go with the green ones), it's an easy job (two bolts) and will help prevent some possible sources of leaks. Also, the O-ring at the receiver should also be replaced.

where can I get the seals and the o-ring ?

Maybe do a search for Carlisleautoair.com
in San Antonio.... if you call there ask for Trey... 20 years doing this kind of stuff.... and talked me out of buying some stuff...
Also check out Aircondition.com
Great forums for AC questions..... mobile or stationary...
They are one of the sponsors for that site also....

Any well-stocked auto store. Just take yours out (use a seal pick), plug the holes in the hoses and back of the compressor so crud won't get in and take one down to match it up. Tell them you want green A/C O-rings to match yours.

You are going to want the proper color Nylog to wet them with when you install them....