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| [GMCnet] Re: A/C Question [message #366318 is a reply to message #366313] |
Tue, 24 August 2021 18:49   |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
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Senior Member |
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Matt,
I think you're probably right -- the flexible coupling to the wobble plate
probably failed. Your note about there being a valve per cylinder pretty
well cinches it -- I don't know why I was only thinking about one valve.
Guess I'll pull it off and tear it down, even before ordering the
replacement, out of curiosity. Fortunately, on the Cad500, it's mounted
right up front in the Vee of the block -- easy to get to.
Thanks,
Ken H.
On Tue, Aug 24, 2021 at 3:36 PM Matt Colie wrote:
> Ken,
>
> If you can see the compressor's clutch drive plate (right there on the
> front)turning when you power the clutch and nothing is pumping, then the
> clutch
> must not be connected to the bevel part (Swash Plate? I forgot the name)
> the makes the pistons stroke. It can't be much else. The valves are all
> individual by cylinder, even if one was jammed, the others would still
> pump something. It is pretty much the same for the pistons, but if one of
> them
> broke loose, I would expect a tell-tale noise.
>
> Unfortunately, the drive plate is mounted to the shaft with a flexible
> element, so you will have a hard time detecting a broken shaft by trying to
> wiggle it. You could put a wrench on the nut and try to spin the and see
> if you feel anything like pumping.....
>
> I have only once had a Sanden open, but there are some good things on
> Sanden's own sight, and a coupled of good YT videos.
>
> If you are sure that the clutch is turning the shaft, there are not many
> choices left.
>
> Please let us know when you find out what happened.
>
> Matt
> Ken Henderson wrote on Tue, 24 August 2021 11:02
>> I need the opinions of those more HVAC knowledgeable than I am: Since
> the pandemic kept us off the road for over a year, I find that the A/C no
>> longer works (equipped with a Sanden compressor and Duracool, it had
> operated without attention for the previous 5 years or so).
>>
>> A couple of days ago, I vacuumed the system down to near 30 in.HG. and
> left it sitting until today, when it was still at almost that level. Then
>> I moved the vacuum hose to a fresh can of Duracool and opened the
> valves. The low-side and high-side gauges both immediately indicated ~95
> psi.
>> Then I started the engine and engaged the compressor. Neither gauge's
> needle even flickered! Repeated compressor clutch cycles yielded the same
>> results: Click-clack of the compressor clutch and obvious rotation of
> the compressor shaft -- yet NO needle movements.
>>
>> I took a brass hammer and rather strenuously rapped the compressor (on
> "hard parts") hoping I might shake something loose inside -- STILL no
>> needle movement with clutch cycling.
>>
>> My diagnosis is that I have one of 3 problems in the Sanden compressor:
> 1. A sheared shaft; 2. A valve stuck open; or, 3. a busted piston -- in
>> that order of probablility. Does anyone, hopefully, have another/better
> idea? Maybe even one that won't require compressor replacement?
>>
>> It's looking less and less like I'll really need A/C in the GMC this
> year, but I'd still like to get it working before I get still older and less
>> able
>> to tinker, so Y'All's opinions will be greatly appreciated.
>>
>> Ken H.
>
>
> --
> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
> GMCES
> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
> Brakes with Applied Control Arms
> SE Michigan - Near DTW - Twixt A2 and Detroit
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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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