Call your local garages.  Most will evacuate your R12 system for free.  They
reuse your R12 in other cars.  Some clowns will try to charge you to
evacuate.
Have a garage pull a vacuum on your system.  You should leak test it first
before paying someone to evacuate a leaking system.  I guess you could
pressurize the system with compressed air to leak check, any better ways to
do this?  After you are satisfied your system is holding a vacuum, add the
134A.  Make sure you add the ester oil before pulling the vacuum.
Good luck, PSD.

-----Original Message-----
From: Dave Mancuso <Mancuso@MTWP.K12.PA.US>
To: Vanagon@VANAGON.COM <Vanagon@VANAGON.COM>
Date: Wednesday, May 20, 1998 11:28 AM
Subject: Re: Vanagon A/C: R-12 to R-134a No-Mod Changeout

>I've seen a R-12 to R134A conversion kit, which contains new refrigerant,
>a can of oil, adapters, and hoses, BUT...
>
>Don't we need to have someone evacuate the system and flush it before
>using this kit? Or can I just put the new stuff in?
>
>Caveat: My system is drained of R-12 over the last couple of years,
>slowly getting warmer--unfortunately, I don't use it much--I should have
>turned it on every 2 weeks like I think Joel recommended once....
>
>Opinions? BTW, I won't vent any leftover R-12 into the air, so that's not
>an option.
>
>--Dave
>
>On 5/20/98 11:05 AM EST, PAT said:
>
>>I have heard the ester oil in the conversion kits protects the compressor
>>seals.  Apparently R12 helps cool and lubricate the compressor better then
>>134A, so R12 systems can get by with a "lesser" oil.  This is purely
>>opinion, from people I have talked to.