[DML] Re: AC clutch running continuously
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[DML] Re: AC clutch running continuously



R-12 isn't illegal. You just can't buy it without a license. R-12 can
taps and gauges are also harder to find now than R-134 (you won't find
them at big box or chain auto parts stores).

R-134 is exactly the same propellant used in those "Dust Off" computer
cleaners, BTW.

The biggest problem with R-12 to R-134 conversions is the size of the
condensor. R-12 condensors are too big. They work, but are not
optimally sized. 

The condensor issue is especially accute with engine mounted radiator
fans. At idle, they can move too little air to compensate for the
oversized condensor. No problem at speed (RPM's as well as natural air
flow), but you can lose the refrigeration cycle while stuck in rush
hour traffic. This is of course no problem for DeLoreans because our
fans are electric.

There's absolutely no difference between R-12 and R-134 compressors.
Just ask anyone who worked at a NAPA or Big A parts house in the
1980's -- both sent stickers to paste on R-12 compressors already
sitting on the shelf to relabel them as R-134. That was the extent of
their conversion.

I think R-134 gets a bum rap for several reasons:
- People improperly convert (biggest sin: not vacuuming the system),
and blame R-134 for their misbehavior. Another big problem is people
adding too much oil, which puddles in the evaporator and won't let
freon in.
- Condensor issue above
- Many people have systems that leak no matter what kind of freon they
put in (where did their R-12 go anyway?). They blame this leakage on
"smaller R-134 molecules" and all sorts of other nonsense. My own
philosophy is: R-134 is so cheap, don't risk damaging the thin wall
copper of condensors and evaporators trying to replace their O rings.
A can of R-134 here and there is a lot cheaper and a lot less trouble
than replacing a ruined component. The exception to this rule is the
compressor, which usually has beefy connections.

You do need to watch what kind of oil you use in a R-134 conversion.
PAG is synthetic, which can react badly not only with residual R-12
mineral oil but some flushing fluids as well (I never realized how
prevalent plain old paint thinner is). Being mineral based itself,
ester oil is perfectly at home with whatever is still circulating.

I run R-134 in all my vehicles, which span the gammut in system
tightness (the worst is a Lincoln that leaks about a can per month).
Temps from the vents are 30-40 degrees, which is plenty cold enough. 

If you want to do your own R-134 conversion, Dave Swingle posted my
methodology to the DMCNEWS.COM website. It's as "incorrect" as can be,
sends A/C purists into paroxysms, but it works. Kind of apropos for my
whole DeLorean, though, which is as incorrect as can be, sends purists
into paroxysms, but is cheap, reliable, and hassle free....

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "welmoedj" <joe.dalton@...> wrote:
>
> I have to disagree with your suggestion not to use 134a.
> If the system is okay and holds its pressure 134a is no problem.
> Yes, the connections and lines are not developed for 134a, but when
> these are checked/perhaps replaced when needed and with the proper
> type of filling (after vacuming) it will provide you with a reliable
> cooling system.
> Furthermore - and I am not an environmentalist - it's better for the
> environment (less poisonously) than R12. Besides that: R12 is
> outlawed!
> 
> Welmoed.
> 




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