[DML] Re: Air Conditioning

["content22207" <brobertson@xxxxxxxxxxxx>]

As the owner of several A/C systems that work perfectly, and which I
DIY myself, I respectfully disagree (about being able to work on them
yourself. Rest of the post is pretty much on target).

Pulling a vacuum is indeed essential. Magic number of 28 some odd
inches was derived at by the vacuum at which water vaporizes at
typical abient temperature (around 90 degrees as I recall). Pulling
that should 100% guarantee that no moisture remains in the system. But
the same thing can be accomplished at lower vacuum if ambient
temperature rises. Not much past 100 degrees and water vaporizes in
the lower 20 inches.

I pull my vacuum's with 460's in my Lincolns (20 or 24 inches,
depending on the model). Given underhood temperatures, that's more
than enough to yield a moisture free system if they're vacuuming
themselves. I use the high compression engine to vacuum the DeLorean.
Haven't had any moisture related problems yet. You could always zap a
system with a heat gun if you wanted to guarantee ambient temperature
was high enough, but I've never found that necessary. Systems are
usually only open long enough to replace expansion valves (Ford)
anyway. DeLorean hasn't been opened since I replaced the compressor.

Your post failed to mention inexpensive and common R-134 as a
refrigerant option. Complete charge costs less than $25.

If it isn't leaking, I wouldn't recommend disturbing the dryer. In
theory it isn't needed anyway (none of my other cars has one, nor does
my household A/C or the refrigerator).

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "David Teitelbaum" <jtrealty@xxxx> wrote:
> It is that time of the year again when we try the A/C and it doesn't
> work! I got several off-list e-mails this week and in the interest of
> the entire list I will repeat several things. A/C work requires
> expensive, specialized tools. You MUST evacuate the system to a hard
> vacuum to remove ALL air (non-condensible gases)and moisture. R-12 is
> hard to come by and it is a crime to waste it (literaly). That said
> there is still some things a DIYer can do. You can get the parts you
> need. You can pressure-test the system by using compressed air
> (assuming there is no pressure in the system so you are not wasting
> any refrigerent). You can remove and replace parts in preparation for
> the A/C shop assuming you can make prior arrangements. You can
> electrically test the system and repair as necessary ahead of time.
> You should insist that the shop checks the oil fill and even replaces
> it. They should replace the service valve cores and any missing caps.
> They should pressure-test, sweep charge, and then vacuum for at least
> 1/2 hour, an hour is better. Fill with a measured charge and
> performance test, adjusting the low pressure switch if needed. If the
> system has ben dead for a long time you "should" replace the dryer.
> One of the more common parts to fail besides the service valve cores
> to slowly leak is the discharge hose. It is the hose that runs from
> the compressor to the condensor core in front of the radiator. On A/C
> systems the rule is to do as little and to disturb as little of the
> system as you can. If a joint is not leaking it is not considered good
> practice to replace the seal "just because". The chances of damaging
> the joint are too high. In general you have to be VERY CAREFUL with
> the fittings. You wind up using large wrenches because the fittings
> are big but you are working with aluminum so it can twist and break
> very easily.
> David Teitelbaum
> vin 10757






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