Freeze-12 and the others like it are around 80% R-134a and 20% HCFC-142b.
The idea behind the mixture is that it will work at compressor pressures
normal to an R-12 system, as opposed to elevated pressures like a straight
R-134a conversion in an R-12 system, thereby avoiding the stress R-134a puts
on the system. If done properly and without complications it should give
comparable performance.
Issues with Freeze-12 are that the mixture can separate (particularly with
extended non-use, like during cold weather when people forget you should run
the system periodically), and like R-134a it doesn't transport oil as well
as R-12 and also like R-134a it can seep through stock/non-barrier hoses
over time. R-134a is also quite toxic, which is one of the problems with the
'it's losing refrigerant oh well I'll just top it off' mentality. These
problems (aside from toxicity) can be satisfactorily dealt with in various
ways, there's quite a bit of information on the 'net.

Cya,
Robert

----- Original Message -----
From: "Geo & Kathleen Hahn" <ahwahnee@CYBERTRAILS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, July 09, 2006 5:40 PM
Subject: Re: Freeze 12 Update

> Maggie Dew wrote:
>
>> ... Through him I found a shop in Albuquerque who will convert the
>> Freeze 12 to R134...
>
>
> Isn't Freeze12 just 134a with some additives?
>
> FWIW, I have used Freeze12 for several years now and it seems okay.
> Living in Tucson the inside temp of a parked vehicle can get to the
> mid-100s so anything that isn't blowing cooled air directly on your face
> will have limited benefit but it seems to work about as well as my
> recollection of R12.
>
> Geo Hahn
>
>
>
> --
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.1.394 / Virus Database: 268.9.10/383 - Release Date: 7/7/2006