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Re: AC coolant phaseout (LONG)

>I understand the federal government has scheduled the production phaseout of 
>freon, R-12, by the end of 1995. I asked a mechanic if the replacement 
>coolant, HFC-134a, caused a problem in the AC system (it does in many 
>systems). All I got out of him was that coolant conversion would be costly. 
>Does anyone know ...
>     1) anyone who has converted their AC to HFC-134a?
>     2) if HFC-134a attacks the AC system enough to require,
>          a) only an upgrade kit (cost? vendor?)
>          b) system component replacement (cost? vendor?)
>          c) other?
>     3) the life of Audi AC systems
>I understand there is an alternative refrigerant (blend),GHG (or R-406a), 
>claiming to be the savior of R-12 refrigeration systems.

>Some now recommend auto AC 
>owners service the systems this winter before the phaseout. What do you 
>think? Comments/thoughts??
>Cameron Duncan
>(Energy Efficiency and Renewable Energy Clearinghouse [EREC]--work 
>(1991 Audi 200S sedan)
>E-mail: cameron.duncan@nciinc.com

I'm far from being a refrigeration expert, or even a reasonably competent
thermodynamicist, but I have gleaned a few facts from reading the available
literature.  In any event, here are the facts as I know them (and I'm sure
that other listerati will jump in to straighten them out where I've gone

There can be material compatibility problems with seals and hoses, so I'd
guess that the minimum amount of change needed to convert an R-12 system to
HFC-134a would be to change these.  Additionally, HFC-134a is not quite as
efficient a refrigerant, so a change in evaporator and/or condenser might be
in order($$$).  Additionally, I have read that accelerated corrosion of the
metallic parts in a converted system is an issue.  I don't know if Audi has
a conversion kit or even a position on conversion.  Perhaps somebody can
jump in here and help us out. 

OTOH, I recall a guy posting a note on Compuserve to the effect that he'd
bought a used late-80's 5000 in which the previous owner had simply
exhausted the R-12, changed to an HFC-134a-compatible lubricant, evacuated
the system, then filled it with HFC-134a.  As I recall, he claimed that
absolutely no other change was made to the system and that it was still
working perfectly after tens of thousands of miles!  One report, though,
doesn't constitute sufficient reason to plunge ahead, IMO.

As for rushing off to either convert your system or to get a last-chance
R-12 top-off, don't worry about it.  R-12 will be available for some number
of years yet.  Although it will no longer be manufactured, it will be
recycled, which is, in fact, required by law.  I'd imagine, however, that
the price will steadily climb, as if it weren't already through the roof.

The use of anything but R-12 or HFC-134a is strictly illegal in automobiles.
The R-406a drop-in replacement for R-12 is approved for stationary
refrigeration systems only.  Moreover, it can be purchased by appropriately
licensed refrigeration technicians only.  If, in spite of this, you manage
to lay hands on some of this stuff, you're on your own.  (I have visions of
motorcycle-mounted EPA Shock Troops using some sort of refrigerant radar,
pulling over miscreants and shipping them off for extended incarceration and
proper indoctrination in eco-think.)  

An equally illegal, but easily purchased refrigerant is a mixture of propane
and isobutane (the mixture ratio, if memory serves, is something like 80/20
by weight), which seems to have few downsides.  It's entirely compatible
with everything in an R-12 system, including the lubricant, boosts cooling
capacity to boot, and is cheap, cheap, cheap.  Because the diffusion rates
of the two components through your hoses differ, however, you can't simply
top off your system as you can with R-12 when the cooling power goes south:
you've got to exhaust the stuff, evacuate, and fill from scratch.  Some will
argue that there is an added hazard of explosion if the stuff leaks, but an
R-12 propelled mist of refrigeration lube will make a mighty impressive
bang, too.  Not to mention what the 15 or 20 gallons of *extremely*
explosive fuel sitting behind you could do, given the right circumstances.

Being an upstanding, law-abiding citizen who is rightfully proud of the fine
young persons of the EPA, I would *never* advocate using an outlawed
refrigerant, or ending a sentence with a preposition, for that matter.
There is a FAQ on the subject of propane/isobutane as a refrigerant lurking
somewhere in the bowels of the Net.  I suppose that a budding eco-gangster
might conduct a Yahoo or Webcrawler search on the keyword "Freon" to locate
it.  I'm sure that no one here would do so, and all will join with me in
condemning such environmental hooliganism.  Wouldn't want to wind up with a
hole in the global warming layer, you know!  ;-)

Hasta luego,