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From: ghg@cidmac.ecn.purdue.edu (George Goble)
Newsgroups: rec.autos.tech
Subject: Re: Any AC techs?
Date: 11 Apr 1995 14:27:05 GMT
Message-ID: <3me3jp$gpp@mozo.cc.purdue.edu>

In article <24.47258.2645@pcohio.com> danny.fitzsimon@pcohio.com (Danny
Fitzsimon) writes:

 >Anyone knowlegeable in charging auto AC systems care to review my 
 >charging procedure, add advice, comments?
 >
 >This is an '85 Toyota Corolla that I've just fixed 4 small leaks on.
 >System has been vacuumed(by me) and is now ready to go. Only thing is
 >I'm getting conflicting opinions on the procedure for charging.
 >
 >Anyway, how about this concensus?
 >
 >Hook up gauges and liquid charge thru the low side w/engine off. Turn
 >AC gauges off. Then procede to turn engine on, warm up and continue
 >with liquid charging till recomended wt. of freon is in. 
 >
 >Thats about it, right?
 >
 >Forgot to mention that I do have a digital scale that measures to the
 >1/2 oz. The system takes a whopping 24 oz. total. 

 
Liquid into high side with engine off.. this reduces two problems.

1) If there is lots of liquid in the low side, esp near the
compressor, upon startup, one can "slug" the compressor
and maybe bust the valves, trying to compress liquid.

2) Newly entered liquid on the low side, may "wash away"
lubricating oil on startup, causing the compressor to run
for a few mins with little or no lubrication, until the
refrigerant and oil mix. Charging on the high side, causes
oil to be returned to the compressor on the first trip
thru the circuit.

Don't charge on the hiside after starting the engine though.
Charge into the low side then.. barely crack open the
manifold valve (if charging liquid), so it boils off
in the hose and doesnt slug the compressor.

--ghg  (inventor of R-406A)

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Freon Type?
Message-ID: <r5r9nusna1bj8vqnf7kjtm520gae5ptm1q@4ax.com>
Date: Tue, 03 Sep 2002 13:24:25 -0400

On Tue, 03 Sep 2002 08:22:30 -0400, Chris Bryant <BryantRV-05@cfl.rr.com>
wrote:

>Richard L. Dillon wrote:
>
>>I just bought a 1986 Sportscoach Pathfinder. It has a Coleman roof air
>>conditioner, which needs charging. I need to know what type freon it takes
>>so I will know where to take it for a charge?
>>
>>Richard

Practically everyone (not you, Chris) has suggested that Richard just toss the
AC because there must be a leak. While I agree that there probably is a leak,
I strongly disagree with tossing the unit.  As long as the compressor and
coils are OK, repairing is much cheaper than replacing.

Richard, there is no charging fitting on that unit from the factory.  The
system is charged at the process fitting (that little stub of a tube sticking
out the side of the compressor) on the compressor, then crimps and soldered
shut to make a hermetic system.  If there IS a charging fitting, then someone
has installed it and that is probably your source of the leak.  A lot of
"professionals" (sic) install piercing valves (also known as saddle valves)
which simply clamp over the line and pierce a hole in the tubing.  Problem is,
the copper tubing and the pot metal valve body have such differing expansion
rates that the gasketed surface eventually loosens and leaks.  I've heard
these things referred to by crooked "professionals" as "service call
generators" for that very reason.

The correct fitting is a silver-soldered in service port.  I usually install
the fitting on the process port, though one can cut the suction line and Tee
one in.  Many "pros" do this wrong too.  There is a shraeder valve in the port
that has rubber or nylon sealing surfaces.  The shraeder valve must be removed
and the body itself kept cool while soldering.  That's too much trouble for
some jakeleg, er "pros" so they just lay on the heat and the service port
leaks.  Another service call generator.

If you're doing this yourself and aren't familiar with the terms, drop me an
email and I'll send you some pictures.

(I shouldn't have to say this but given some of the room temperature IQs of
people in this group.... None of the comments about "pros" in any way
references Chris who IS a pro.)

>
>	It's R-22, but I agree that you would be throwing your money
>away to have it recharged. If it is empty, it has a leak, and the new
>refrigerant will quickly leak out, and most people do nit charge them
>correctly- IMHO, the *only* way to charge is with a scale (they hold
>under 1 lb of R-22)- and most guys will not take the time the charge
>it properly.

Of course, a charging cylinder will do the same thing and is handier in many
cases.

Another tip:  If the condensing temperature is the same as the system
ordinarily operates at (block the airflow if necessary), one can nail the
charge weight within 5% or better using a mechanic's stethoscopes.  Simply
apply the stethoscopes to the metering device (the evap end of the cap tube in
this case) and listen while charging.  You'll hear the gas flow sound change
to a gurgling as liquid and vapor bubbles mix, then to the sound of flowing
liquid as the correct charge is reached.

I've checked this against my scales often enough to know that I can nail the
charge dead on if the condensing temperature is normal.  If the condenser is
cold (charging in the winter, for example), this will result in over-charging.
For rooftop units (RV and commercial) it's much easier to carry a stethoscopes
and a hunk of cardboard (to block the condenser air flow) than scales, extra
hoses and in my case, a long extension cord for my line-operated scales.

John



 
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