Re: [DML] R134a retrofit
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Re: [DML] R134a retrofit

Before recharging a dead system with ANYTHING a good shop will find
and repair any leaks. In fact it is the law. On the subject of
converting to R-134A, early on there were not many good "drop-in"
replacements so a lot of shops tried to convert the older R-12 systems
over to -134. There are a lot of mixed results. Some systems seem to
tolerate the conversion better than others. A lot depends on the
compressor, the kind of oil, and how contaminated the system is at the
time of conversion. The -134 definately makes the compressor run
harder (higher head pressures) and there is some loss of cooling
capacity because the sizing of the coils is smaller for -12 which is
more effecient than -134. The horror stories of the oil turning into
gunk does not seem to be the general case (unless the system is
heavily contaminated).
 My opinion is that with several good drop-in replacements available
now for R-12 there is no reason to lose capacity switching to -134. I
do strongly recomend ALL leaks be fixed, the system flushed, the
service valves be replaced, and the oil changed. The system should
then be completely evacuated to 700 microns for an hour before being
recharged. R-12 can still be obtained. It is expensive but not so
expensive as to be prohibitive. The bigger cost in doing A/C work is
still the labor. You only need about 2 1/2 lbs of the stuff so at $60
a lb you are only talking about $150 for the refrigerent. BTW any
good, competant shop can find leaks. Generally if it is difficult to
find a leak it is usually the evaporator coil. The more common areas
of leakage are the service valves and/or the discharge hose. I like
leak-test solution, aka soapy water. It doesn't stain or cause a mess,
works with the fans running, and doesn't give false positives. It also
provides positive indication of the location AND the amount of leak.
David Teitelbaum
vin 10757

--- In dmcnews@xxxxxxxxxxxxxxx, Soma576@... wrote:
> Nathan,
> I have done a cheap-o conversion to R134A with mixed results.  
Basically I 
> just had the system sucked down for about an hour, then ports 
changed and 
> reinstalling with 134A and compatible oil.  Didn't take the 
compressor apart or 
> replace any O-rings or anything.  It blows nice and  cold when it is
> charged, but I need to get it recharged every year or two  because
apparently too 

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