[DML] Re: Air Conditioning

["Harold McElraft" <hmcelraft@xxxxxxx>]

I would suggest a couple of things if one has a system completely 
down and going for R-12. (BTW it is a FEDERAL crime to release R-12 
into the air intentionally - thus the need for special equipment.)

If a system has been restored and can hold a vacuum of say 29.13 In. 
Hg you are probably safe to then charge.(29.13 is the boiling point 
of water at 70 F. before altitude adjustments) I'm not sure I would 
recommend pressurizing with air because a killer of AC systems is 
moisture. The accumulator has a bag in it to assist in trapping any 
residual moisture. Exposing this to air will ruin it. The vacuum 
takes moisture out.  Not just any vacuum pump can pull 29+ In Hg 
either. The vacuum pump should run for at least 50 minutes after the 
full level is reached. Most mfgrs of AC parts recommend 90 minutes. 

With a system completely open I would replace the orifice tube and 
accumulator for sure and probably the low pressure cycling switch 
too. Just add one ounce of mineral 500 refrigerant oil to the 
accumulator when you replace it. (R-12 assumed here).

The AC system is so multi dependent on everything working to get 
good cold air it is important to check fans, duct door operation, 
etc to get the max from your system.

Harold McElraft - 3354


--- 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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