[Supras] No AC on 86.5 MkIII w/ R134A conversion

[Hacker J]

No, I would say that is good advice, although you just want a few bubbles, not a frothy mix. Its
also temp sensitive, so a few bubbles at 70degF will probably be many bubbles at 80degF.  Try to
fill when the ambient temp is near the average for when you use A/C in your area.

Most experts say the R134A conversions should be slightly undercharged for maximum performance.
The sight glass lets you look at the exit gas/liquid from the bottom of the condenser. One of the
concerns with R-134a is that the high-side pressures are a bit higher at any given temperature, so
condenser efficiency is critical to good system performance. The condenser should really be bigger
for it to work at best efficiency, but such is life when the system was designed for R12.

With the sight glass showing bubbles, it means that almost all of the hot gas from the compressor
is being cooled enough to condense into a liquid. The gas bubbles are simply gas that hasn't been
cooled enough. With stable system pressures and temperatures, and with minimum air in the system,
the sight glass indicates the state of charge in the system also.

Jon

--- Jim Wooden <Jim at WoodenU.com> wrote:

> Thanks Jon!
> 
> I was told that AFTER conversion there would be bubbles in the sight 
> glass as to clear the bubbles would result in an over-fill when using 134A.
> Is that BS?
> I have to say that even when it was working correctly there were 
> still bubbles after conversion.
> 
> At one time I had a chart for R-12 that showed typical hi & low side 
> pressures vs. operating conditions ... still not ideal but would at 
> least get a guy close....
> 
> Thanks for your help!
> Jim
> 
> 
> 
> At 02:34 PM 3/28/2008, Hacker J wrote:
> 
> >The pressures will depend on heat load, humidity, compressor speed, 
> >and ambient temperatures, so
> >nothing can really be said there.
> >
> >The sight glass needs to be free of bubbles during operation 
> >indicating that the high side is
> >fully condensed.  Toyota has never released any data on the 
> >subcooling temp, and the superheat is
> >set by the TXV in the evaporator, so really the sight glass is all 
> >you can go by.
> >
> >Jon
> >90T
> >
> >
> >
> > > > From: Jim Wooden <Jim at WoodenU.com>
> > > To: Supras at supras.com
> > > Date: Fri, 28 Mar 2008 09:02:15 -0400
> > > Subject: [Supras] No AC on 86.5 MkIII w/ R134A conversion
> > >
> > >
> > > Well some years back I converted my AC to the R134A as, at the time,
> > > R12 was very expensive and I had some leaking o-rings that required
> > > disassembly of the system.
> > >
> > > On the advice of a mechanic buddy that had done a number of these
> > > conversions we did the "simple" conversion which consisted of adding
> > > PAG oil and "special additives" via a kit from Quest then recharged
> > > with recommended amt of R134A
> > >
> > > Worked fine for two years then just didn't seem nearly as cold any more.
> > > I took it back to him and, finding no serious leaks, he just hooked
> > > up the AC machine pumped it down and loaded a fresh charge.
> > > Well... its two years later AGAIN, and although there is still some
> > > charge in the system (sight glass shows pretty full) I get ZERO cold air.
> > >
> > > I have heard the R134A cars (esp. the conversions) are much more
> > > sensitive to being low on charge, and that could be the case here...
> > >
> > > Does anybody have the recommended high-side/low-side pressures for a
> > > MkIII R134A conversion handy?
> > >
> > > Other suggestions appreciated also  ;-)
> > >
> > > Thanks,
> > > Jim W.
> > > original owner 1986.5 MkIII
> > >
> >
> >
> >
> > 
> >____________________________________________________________________________________
> >Never miss a thing.  Make Yahoo your home page.
> >http://www.yahoo.com/r/hs
> 
> 



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