CLUTCHED compressor shear pin?

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PromiseRing
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CLUTCHED compressor shear pin?

Post by PromiseRing »

2013 Mazda CX-9 3.7 with rear AC, 203,000 miles.

Greetings, looking for some insight on a friends 2013 Mazda CX-9. When AC button is pushed, I can watch the compressor clutch engage, fans kick on, but absolutely no pressure change occurs on the gauges.

I have dealt with clutchless AC systems utilizing a variable displacement compressor that had seized, shearing something internal which would allow the engine to continue running without breaking the serpentine belt. In that instance, I had the same occurrence of no pressure change.

I am unfamiliar with this Mazda compressor, I believe it is a Denso 10S20C model. Perhaps this system uses a clutch but also a shear design? Hoping someone more knowledgable will know, thanks! :mrgreen:
PromiseRing
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Re: CLUTCHED compressor shear pin?

Post by PromiseRing »

Oh, and the thought of a slipping clutch did cross my mind as well. As did a stuck open metering device, but I cannot see that allowing zero pressure differential.
PromiseRing
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Re: CLUTCHED compressor shear pin?

Post by PromiseRing »

Okay, answered my own question. I removed the fender liner so I could stare directly at the compressor. There's a rubber dampener between the compressor shaft and the outer portion of the clutch. That dampener has broken free from the compressor shaft. So even though the compressor clutch is engaging, the compressor itself is not spinning.

I grabbed the compressor and was able to spin it. It is not seized.

My question for you guys now is, would you make the call to replace the entire compressor assembly, given the mileage, or opt for just a clutch replacement? My gut is telling me to replace the compressor, R/D, and both TXVs.
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Tim
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Re: CLUTCHED compressor shear pin?

Post by Tim »

It's a piston compressor, so there is no internal control valve. Zero pressure and hub turning, possible broken shaft.
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tbirdtbird
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Re: CLUTCHED compressor shear pin?

Post by tbirdtbird »

Go with your gut
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JohnHere
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Re: CLUTCHED compressor shear pin?

Post by JohnHere »

I vote for replacing the compressor assembly, especially with that amount of mileage on it, as well as the condenser and the receiver/dryer, which I believe is integral with the condenser.
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PromiseRing
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Re: CLUTCHED compressor shear pin?

Post by PromiseRing »

Hey guys, so I have the old compressor out. Oil looks healthy, no metal. But upon trying to weigh the old compressor oil (I KNOW I should have used volume instead of weight :oops: ), I was only able to get roughly .8oz out. I'm sure if I tried long enough I could get closer to 1oz out, but I was expecting to see something more like 4oz.

The compressor provided to me comes pre packaged with 5.4oz of pag 46. It says if the vehicle has rear AC to add 4 more fluid ounces. I'm extremely apprehensive to add so much more oil to this. What say you guys, listen to the manufacturer who knows what they're talking about? :lol:

No evaporator was touched in this repair.
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Re: CLUTCHED compressor shear pin?

Post by tbirdtbird »

More info please...
Remember that in a bare metal installation that 5.4 oz will end up being distributed through the entire system.
So, evaps not touched....was condenser changed out? F/D? Any parts flushed/blown out?
Some of your old comp oil is in other places....that needs to be factored in to the new 5.4 you have and the extra for the rear.

ie Calculate (guess) how much oil remains in all the components and then subtract from the 9.4 that would be used in a bare system.
Last edited by tbirdtbird on Fri Sep 09, 2022 9:11 pm, edited 1 time in total.
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JohnHere
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Re: CLUTCHED compressor shear pin?

Post by JohnHere »

My guess—and this is merely a guess—about how much oil is in the system now:

Two fluid ounces in each evaporator, 2 fluid ounces in the condenser, 1.5 fluid ounces in the R/D, and 1.5 fluid ounces in the lines and hoses (taking into account that the lines for a front-and-rear A/C system are considerably longer than a front-only A/C system.) That sub-totals to about 9.0 fluid ounces, not including the small amount of oil that came out of the old compressor. Presuming that you drained out about 0.8 fluid ounces from the old compressor brings my guesstimated grand-total to about 9.8 fluid ounces.
PromiseRing wrote: Fri Sep 09, 2022 4:31 pm The compressor provided to me comes pre packaged with 5.4oz of pag 46. It says if the vehicle has rear AC to add 4 more fluid ounces. I'm extremely apprehensive to add so much more oil to this. What say you guys, listen to the manufacturer who knows what they're talking about?
Based on my guesstimated calculations above, it sounds like the compressor manufacturer is presuming all new parts and/or a completely clean and dry system—that is, a system with no oil in it whatsoever. So adding together their recommended amounts: 5.4 ounces plus 4.0 ounces equals 9.4 ounces—pretty close to my guesstimated total amount.

All told, if I were working on this, I would drain out the 5.4 ounces of factory oil from the new compressor and add back 1.5 ounces of PAG-46. At the same time, I would add 1.5 ounces of oil to a new R/D, 2 ounces to a new condenser (or 3.5 ounces to a new condenser having an integral R/D), and call it good.
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