This has been covered exhaustively in one way or another over the past few
months and generally every spring and early summer; you can search the
archives here:

http://gerry.vanagon.com/archives/vanagon.html

If you are saying that you have enough R-12 to charge the system on hand,
then I would set the system to rights (fix leaks, etc.) and use up the R-12.
If you put R-134a into the system without following the proper conversion
process then you are likely going to bollocks up the works, requiring
extensive and costly rehab, unless you are particularly lucky or you own a
Bronco II, apparently (j/k Daryl).

In my experience, doing something 'without doing nothing' is almost always a
recipe for disaster.

Cya,
Robert

----- Original Message -----
From: "Sharon Mendonca" <bobonsharo@SBCGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, July 01, 2005 3:25 PM
Subject: What happens if you put 134a into a r12 systems without doing
nothing?

> Two mechanic told me to go ahead but I still have a problem!
>
> I have both kinds and ready to put either into A/C.
>
> Any thoughts??????
>
>
> Bob