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| [GMCnet] A/C Problem [message #359234] |
Wed, 07 October 2020 16:40  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma:
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A couple of days ago, I got the GMC out and washed it, top to bottom. I'm
not sure the roof had been washed all over since the 2002 paint job!
Needless to say, it was DIRTY! Dawn mixed with lots of water and 83 yo
elbow grease finally got it looking pretty good.
Then yesterday I got inside, only to find lots of mildew. Seems sitting
closed up since 26 November 2019 wasn't its favorite condition. I got most
of that, including every square inch inside and outside of the
refrigerator, cured with Lysol wipes and more elbow grease.
Today I tried the TroyBilt generator. 10-15 seconds of cranking had it
running like a top and it was happy to power the roof air conditioner.
Then I went to fill the gas tanks (24 gallons) -- nope, I didn't top them
off before parking it. That's when I found out that the dash air no longer
produces even cool air. When I parked it last November, it was cooling
well. Perhaps needed a little more Freeze 12 but not bad at all for having
been untouched for 5 years+. But today, NO cooling. So, the refrigerant
must have leaked out, right? I've got a pretty good manifold set, and I've
used it a number of times over the past 15-20 years. And I've rebuilt,
redesigned, and repaired several auto A/C's -- but I'm NO EXPERT! I've
been lucky -- all the bits and pieces I've used have all worked, except for
the odd seal, hose, or belt which anyone could find and replace.
When I connected the manifold set, the high and low gauges, as expected,
read the same. I was a bit surprised to see 95 psi static, but so be it.
Then I started the engine with the A/C turned on. Still reading the same
on both gauges! Still about 95 psi! Hmmmm... I finally realized (with
being able to see it) that the compressor clutch was not engaging. Jumping
power to it directly from the chassis battery, I could hear the clutch
engage and the engine pick up a little load. But I saw essentially no
change on either pressure gauge!
Finally, I connected a fresh can of Freeze 12 to the filler hose. Opening
that caused the low pressure to rise sharply -- with no effect on the high
pressure side. Later, I disconnected the Freeze 12 and bled off most of
the pressure on the low side -- still no effect on the high side. Opening
the high side slightly caused a slow drop in that pressure -- I didn't
drain off much. It sits now with maybe 20 psi on the low side and 85 psi
on the high side -- after an hour or more unattended. The inside of the
coach is nice and cool -- with the roof air running on shore power!
SO, what say ye? What's plugged? I've never heard anything abnormal
sounding from the Sanden-clone compressor I've been using for about 10
years, so I find it hard to believe it's failed internally. But if not,
why is there no change in any pressure when I can tell it's running?
Where's the energy that the engine's obviously putting into it going?
Nope, the gauges are not stuck -- they respond perfectly normally.
After determining it was 111*F outside, I quit (only to have the
thermometer say it's only 91*F). I've no idea whether to attack the
thermo-expansion valve or the compressor or ???. Sure hope one of you
more-experienced A/C experts has an idea.
Thanks!
Ken H.cwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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