>------------------------------
>
>Date:    Thu, 7 Sep 2006 16:14:15 -0500
>From:    John Rodgers <inua@CHARTER.NET>
>Subject: Re: a/c - Sorry
>
>In reading the rules, here is my understanding of this AC thing.
>
>You can ONLY convert to 134a directly from R12. You cannot convert
>DIRECTLY to anything else. To convert to 134a requires certain steps for
>safety and the simple mechanics of the process. But VERY importantly,
>the inlet and outlet filler valves have to be changed from R12 type to
>134a type, and a tag has to be put on the system in a visible place
>saying it has been converted and has 134a in the system.
>
>The rules don't say that you can't convert to another refrigerant at
>this point. They don't exactly say you can, but they don't say you can't
>either. But they do say that IF you convert to one of the approved
>alternate refrigerants like Freeze 12, you must follow procedures
>prescribed and also change one valve - I think it is the fill valve
>connection - back to that of R12.
>
Mostly correct.  You have to change the service connections to Freeze-12
fittings.  Each refrigerant has to have its own fittings, and the
vehicle has to be labeled as to which refrigerant is installed.  Also,
if the receiver/drier is fitted with a high pressure relief plug (very
likely), then the system has to be fitted with a high refrigerant
pressure compressor cutout switch (the vanagon high refrigerant pressure
switch - at least 1986-88 - turns on the high speed radiator fan, and
the radiator high temp switch cuts off the compressor, which doesn't
legally qualify).

There are a number of downsides to Freeze-12:

* It is a blend of R142a and 134a, and therefore may leak out/diffuse at
different rates, so 'topping off' may change the mixture (and cooling
efficiency)  over time.
* Freeze 12 is not very good at carrying mineral oil, and the system
really should be flushed, the receiver/drier replaced, and the system
filled with PAG/POE oil before charging.
* Freeze 12 has to be recovered with dedicated equipment, so you should
make sure there are a sufficient number of shops in your area that have
recovery equipment, or you'll be hosed when you need some repair.
Freeze 12 *must* be removed prior to mechanical servicing, so you have
to have someone equipped for Freeze 12.  Depending on where you are,
might be a problem or might not.

That said, Freeze 12, when properly retrofitted, works very well, and
much better than R-134a.  And like with R-12, you have to have an EPA
608/609 license to buy it.  You can get certified on line through MACS,
at http://www.macsw.org/certification.php.

Keith Hughes
'86 Westy Tiico