GMC A/C

[Ken H.]

I finally got around to testing the GMC's A/C just now. It had been so
long since I'd touched one that I'd almost forgotten the little I once
knew. But, after I wired up a way to remotely control the compressor
clutch, I connected the manifold set, including a can of Duracool. When I
cranked the engine and opened the low side manifold valve to the Duracool,
the low gauges went to about 90 psi -- and essentially stayed there no
matter what I did. No change on the high side. Until I let Duracool
pressure into the high side, then it went 90 psi and stayed there. After
that, engaging and disengaging the compressor had no effect on either side
-- and I could see the compressor shaft turning. Bleeding pressure from
the low side had no effect on the high side.

I didn't fill the system with Duracool since the compressor didn't seem to
be doing anything. Perhaps I should have added 3 cans?

Unless I'm badly mistaken, I need a replacement compressor, but I'm
certainly open to suggestions!

Ken H.

 

[Matt Colie]

Ken,

Just be clear.
You could see the compressor shaft turning and the high and low pressures did not change??

If it is still an A6 Delco pump, that just can't happen unless shaft is broken inside or the entire guts have been ripped out of the pump......
Just for grins, with things shut down, try turning the drive plate on the front of the compressor by hand and see if you feel any resistance at all.

I would love to know what happened. I am witnessed some A6 in real bad shape, but never that bad.

Matt
--
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

 

[Ken H.]

Matt,

I just went out and checked: Yes, with the engine cold, I can turn the
compressor shaft by hand, either direction. It's "not hard, not easy"
tight.

I was able to find the almost-obliterated label, remove, restore, and
photograph it. Much to my surprise, it IS a Sanden, not a clone. SD508
Model 5411. I even have its serial number! There are now numerous clones
of it available, and Sanden has a direct replacement, so if necessary, I
should be able to replace it easily.

Ken H.

> Ken,
>
> Just be clear.
> You could see the compressor shaft turning and the high and low pressures
> did not change??
>
> If it is still an A6 Delco pump, that just can't happen unless shaft is
> broken inside or the entire guts have been ripped out of the pump......
> Just for grins, with things shut down, try turning the drive plate on the
> front of the compressor by hand and see if you feel any resistance at all.
>
>
> I would love to know what happened. I am witnessed some A6 in real bad
> shape, but never that bad.
>
> Matt
> --
> 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
> _______________________________________________
> GMCnet mailing list
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>

 

[roy keen]

I would say your valves are not seating (stuck open?) a broken crankshaft or a broken rod. At any rate the compressor has a bad mechanical problem.
--
Roy Keen
Minden,NV
76 X Glenbrook