Date:         Mon, 20 Jul 2009 17:56:05 -0700
Reply-To:     Keith Hughes <keithahughes@Q.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Keith Hughes <keithahughes@Q.COM>
Subject:      Re: AC System Repair/ Upgrade
In-Reply-To:  <BAY0-PAMC1-F10jprLd0000a41b@bay0-pamc1-f10.bay0.hotmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

> Date:    Mon, 20 Jul 2009 14:28:21 -0700
> From:    Robert Fisher <refisher@MCHSI.COM>
> Subject: Re: AC System Repair/ Upgrade
>
> I've read a number of posts here and elsewhere where people have done this
> and it worked for the short term, but I've also read as many posts where it
> completely screwed up their system, due to the incompatibility of the
> chemicals. If there's enough of the old R12 stuff in there you'll get a
> nasty goo that will play hell with your A/C system.
> The OP said it most recently had R12. BTW, if it's leaking R12 it'll leak
> R134 or Freeze-12 even faster. Better to do it right to begin with.
> If you have, or have access to an air compressor, you can get the rest of
> the tools to do it yourself for under $100. The whole thing might run $200
> with flush, oil and refrigerant.
>
> Cya,
> Robert
>
Well, my $0.02 worth:  Number 1, never put anything in the system except
refrigerant.  Stop-leaks will eventually sludge up compressor valves and
expansion valves, and foul drier media.  Number 2, R-134A is NOT
miscible with mineral oil.  What that means, is that the oil will not be
carried through the system with the refrigerant, and compressor failure
will result - just a matter of time.  The PAG and POE oils that are
miscible with R-134A are not compatible with mineral oil, and ugly stuff
will result, and once again, compressor failure will result - just a
matter of time.  Number 3, Freeze-12 does *seem* to work OK, but only
the R-142 fraction is miscible with mineral oil, so expect less
compressor oiling.  Also, being a mixture, when half leaks out - likely
fairly quickly - you'll need to evacuate first and then charge since the
constituents will not leak out at the same rate (the 20% that is R-142
will leak out faster than the 80% that is R-134A).  If you just refill,
your 80/20 mixture becomes maybe a 90/10 mixture, and your cooling takes
a dive.  And good luck finding a shop to evacuate the Freeze-12, since
they have to have dedicated recovery equipment.  Used to be some around
here in Phoenix, but AFAIK they're gone now, just not enough R-12
equipment around to support the extra overhead.

So, best course IMO is to either fix your leaks and recharge with R-12
(and if you've used dyes and stop leaks, flush the system, replace the
drier, pull the compressor and drain it so that you can put in the
correct amount of oil, and use PAG oil in the system) - the best
performance option, or convert to R-134A (fix/replace hoses, drier,
expansion valve, flush system, recharge, and expect poorer performance
unless you upgrade the condenser).

Keith Hughes
'86 Westy Tiico (Marvin)