Denso compressor hard to turn

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GregB
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Joined: Sat Jul 07, 2018 9:34 pm

Denso compressor hard to turn

Postby GregB » Sat Jul 07, 2018 9:55 pm

Hi all,

We have an '06 Sienna with a Denso 471-1010 compressor, I believe this is of the 10S20C type. The air conditioning is working fine - nice and cold front and rear air. However, once the engine is well warmed up, the compressor can engage with a bit of a thud, and even after letting pressures equalize, the compressor hub can be very difficult or impossible to turn by hand. It doesn't feel like a dragging clutch but maybe a dragging piston inside the unit. This evening I was able to turn it a quarter turn and no more - like something was sticking inside the unit. Not a metallic grinding feel, but just sticking and refusing to be turned further. We decided to continue driving on our road trip with the AC turned off despite the heat.

Is this normal behavior from these units, or am I looking at needing to replace this before it seizes or worse? How much debris if any can I expect to find inside the refrigerant loop?

- Greg
GregB
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Joined: Sat Jul 07, 2018 9:34 pm

Re: Denso compressor hard to turn

Postby GregB » Mon Jul 09, 2018 11:38 am

Additional information:
- once the vehicle cools off completely, the compressor (10S type) turns relatively easy by hand, without binding, though not quite as easy as two other Denso compressors I have access to (a very similar 10PA type with 360K miles on it and a variable displacement 7SBH type). If I turn it on at that point, it engages quietly and runs quietly.
- no pressure readings yet. I have not yet hooked my gauge set up to this vehicle. But no complaints with the AC operation - it cools great.
- this vehicle has an inline mesh filter integrated into the receiver/drier that is a part of the condenser unit.
- if the compressor is indeed going bad, my sense is to replace the compressor, the discharge line (has a muffler), and the condenser / receiver / drier / inline filter assembly. Observations re. the condition of the oil / lines / etc may dictate whether more work needs to be done.

Greg.
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bohica2xo
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Re: Denso compressor hard to turn

Postby bohica2xo » Mon Jul 09, 2018 2:24 pm

How many miles on the '06 Sienna?

Any history on the vehicle? A/C service? 1500 hours of soccer mom idling?

The condenser is the primary filter. The screen is there to tell you how much trash made it all the way through. The good news is OEM Denso condensers are cheap & available. Good call on the discharge line, 40 bucks to get rid of a muffler full of trash is a bargain.
GregB
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Joined: Sat Jul 07, 2018 9:34 pm

Re: Denso compressor hard to turn

Postby GregB » Mon Jul 09, 2018 2:55 pm

136K miles on the Sienna. We just acquired it two weeks ago, but we know the original owners. The vehicle is well-maintained but "grew up" in the humid southeastern US, so lots of AC use most of the year. Probably 75% of the miles are around-town driving. No previous repairs to the A/C.

Greg.
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bohica2xo
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Re: Denso compressor hard to turn

Postby bohica2xo » Mon Jul 09, 2018 3:50 pm

Generally a system leaks refrigerant as well as oil - generally. We have seen instances where either item leaked out without losing much of the other.

A system that has been "topped off" a couple of times will be somewhat low on oil. It kind of sounds like your compressor is trying to seize when hot, more common for low oil than high mileage.

Any oily spots on the A/C plumbing? Rear A/C vehicles have a lot of tubing to check...
.
GregB
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Re: Denso compressor hard to turn

Postby GregB » Mon Jul 09, 2018 4:05 pm

I would think an oil-dominant leak would be from a low spot in a component that tends to retain a pool of oil - compressor case, condenser, evaporator, drier. I'll have a look.

Greg.
GregB
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Joined: Sat Jul 07, 2018 9:34 pm

Re: Denso compressor hard to turn

Postby GregB » Mon Jul 09, 2018 5:05 pm

The system looks perfect on the outside. All visible lines and fittings are dry, compressor is dry, evap drains (front and rear) are dry, condenser is dry. I did not remove the clutch to check the shaft seal, but there's no evidence of oil being slung around.

The previous owner says they've never had the A/C system serviced, not even just to top off refrigerant.

Your comment about low oil makes tons of sense though. I'll try to get my gauges on this soon to check pressures & also attempt to measure the liquid line temp & suction line temp to get subcooling & superheat readings to see if anything might be contributing to poor compressor lubrication (low r134a charge or a TXV open too far under low thermal load would be my first guesses).

Greg.
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bohica2xo
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Re: Denso compressor hard to turn

Postby bohica2xo » Mon Jul 09, 2018 6:30 pm

City vehicles pick up a lot of hours. The lifetime road speed average for a taxi here in Las Vegas is 15 mph. That means at 136k the accessory drives have 9000 operating hours. Around here it is easy to find a Crown Vic taxi retired around 240,000 miles & still on the road. I pulled a core alternator out of one that was original, and still charging - loudly.

Could be that your compressor is just worn, and that oil that has been making the trip through the loop since new is not up to the job any more either.
GregB
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Re: Denso compressor hard to turn

Postby GregB » Sat Jul 14, 2018 5:12 pm

Here are the readings: 30°C (86°F) ambient, 40psi low, 220psi high, fans (both) high, air recirc (to avoid sucking in engine fan air), windows slightly down to keep the heat load up, RPM 1000, and subcooling varied between 2°C and 7°C (4°F and 13°F) depending on the conditions.

I was able to force the compressor discharge up around 350psi by throwing a blanket over the vehicle's fascia.

Looks like a modest undercharge; I'll probably take the vehicle in to have a recovery & recharge with a bit of PAG46 injected, and then reevaluate the compressor.

Greg.
GregB
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Joined: Sat Jul 07, 2018 9:34 pm

Re: Denso compressor hard to turn

Postby GregB » Wed Jul 18, 2018 11:02 pm

Update: I had a free check done on the AC by a nearby shop to get another opinion, and the tech there, while a bit unsure, didn't think we needed to do anything to the compressor at this point. I added 1oz of oil and about 8oz of r134a this evening, with perhaps a bit of improvement in how easy the compressor is to turn when hot. I think we'll call it good for now, monitor it, & revisit making a repair if something seems to gets worse.

Greg.

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