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2007 Chevrolet Malibu 3.9 a/c problem compressor turns but

no cooling pressures are about...
2007 Chevrolet Malibu 3.9 a/c problem compressor turns but no cooling pressures are about the same I replaced compressor thinking broken crank in it but the new AC delco compressor in the box , on the bench when you turn it act the same way put your finger over the suction side and turn the shaft it acts like it has no suction either am I missing something here.
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Customer reply replied 2 months ago
it is a Cvc compressor
Answered in 1 hour by:
9/22/2017
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4,831
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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The compressor has a control valve built into it that modulates pressure. Don't judge it based on bench testing, have you installed the compressor and tried it yet?

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Customer reply replied 2 months ago
I put a new Delphi in and can't get any cooling I flushed all the lines and put a new condenser in and charged to 1.1 pounds also I measured in five ounces of oil

OK, I was unclear whether you actually installed that new compressor or not.

The only thing that makes any sense here is that the expansion valve is stuck in the full open position. If the compressor is engaging, and the pressures are close to equal, the expansion valve has to be open. I am assuming that the pressures change at least a little bit when the compressor comes on, no?

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Customer reply replied 2 months ago
I replaced the expansion and still the same thing when you switch the a/c on the suction goes down for split second but the returns to almost equal suction/discharge pressure you rev it and it comes down 3or4 psi the pressure are about 80 give or take depending on outside ambient temp

It's possible that there is too much oil in the compressor, 5 ounces a lot of oil. Not sure how this would impact what you're experiencing, but I'm looking for the things that seem out of place. 5 ounces is too much. How much oil did you drain from the old compressor?

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Customer reply replied 2 months ago
I think even if the expansion valve was open all the way it would still be metering something and causing high pressure an some low pressure differential it's as if the compressor is stuck in no displacement mode I tire the original compressor apart and other than worn out pistons nothing was broken
Customer reply replied 2 months ago
When I flushed the system and replaced components there would be zero oil in the system the Delhi sheet said total oil charge 5 oz. we drained the compressor measured and re filled with five ozs.

And you're sure the clutch is staying engaged, not slipping, etc? This doesn't make any sense if the compressor shaft is turning and the compressor is doing nothing at all.

I have seen expansion valves stick wide open and cause this problem, it's the only explanation, really. Pressure exists on one side of the system because of the restriction the expansion valve/tube provides, and in the case of expansion valves, because they are designed to move, they are always suspect. Fixed orifice tubes rarely fail in this manner, they get clogged up, if anything.

If you are certain that the clutch is staying engaged and not slipping, try tapping on the expansion valve and see if that makes any difference on the gauges.

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Customer reply replied 2 months ago
Did this expansion get updated the original part number is ***** the one I bought was from oreilly

I don't have a part number update history, but I can tell you that the GM part number for the replacement is 52495729.

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Customer reply replied 2 months ago
Oh boy getting a headache replacing the expansion valve now keep you informed

OK

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Customer reply replied 2 months ago
I tried a Napa expansion valve still the same about 95 psi on head and 60 or so on suction. But when I started it the suction started going down and cooling but after 10 seconds the low side pressure started rising and cooling went away

Is the liquid line cold where it enters the expansion valve?

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Customer reply replied 2 months ago
No it's probably about 85 or so

I'm curious what happens if you overcharge the system. If you add 8 oz more refrigerant, what do the pressures do then?

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Customer reply replied 2 months ago
I can't add because car pressure is the same as vessel pressure unless I were to use the recovery machine and force it in

I can usually add to the low side while engine is running, you can't even do that?

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Customer reply replied 2 months ago
No I can't if I got the torch and heated the 30 pound vessel I could n can you force the compressor to go to large displacement mode

No, the compressor does this internally, there is no outward way to change the stroke.

Don't put a torch to the 30lb cylinder. A heat gun might be a better idea. But this is all just academic anyway, I was curious how it would react if it was overcharged, but it's not worth spending half a day to do it.

I like to charge the low side with the engine running. What if you discharge it, vacuum it, then start the car and charge it through the low side? I wonder if you could overcharge it then?

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Customer reply replied 2 months ago
The problem is I can't get the suction pressure/temp down s the car runs and gets hot the pressure naturally rises currently if I run the a/c high side is 120 low is 85 off they equalize at bout 100 psi

That is crazy. The control valve in the compressor has to be faulty, after two expansion valves doing the same thing.

What caused this to happen in the first place, was there a collision or compressor failure, how did it end up like this?

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Customer reply replied 2 months ago
Don't know car came in not cooling compressor ran but no cooling little movement in gauge I thought broken crank in compressor took apart and just tired pistons nothing broke installed me Delphi compressor condenser expansion valve manifold GM hose set flushed the rest vacccumm 30 minutes and like nothing has changed the expansion valve I used look just like GM denso,oreilly,Napa and nothing changed
Customer reply replied 2 months ago
Even if the compressor was in low stroke mode wouldn't we see cooling or more pressure differential
Customer reply replied 2 months ago
I also noticed after recovery that I sucked out about 1 oz of oil out of the system so I don't think it's oil charge problem

I understand, and I agree, although oil charge isn't high on my list of suspected problems.

So, this car came in like this, and nothing you've done has changed it. That's remarkable. And weird.

I just reviewed the trouble tree in the GM service manual, to make sure I wasn't missing something here. It's either a malfunctioning compressor, or it's undercharged. Seems like the one variable we're not addressing here is equipment problems, how certain are you that you're getting 1.1 lbs of refrigerant into this car?

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Customer reply replied 2 months ago
All right so switched valve in compressor started filling from suction side weighting in still the same thing any ideas can't wait till beer thirty
Customer reply replied 2 months ago
Oh I used two different scales

Even GM is lost on this. The trouble tree says faulty compressor or undercharged. We've covered everything here that I can think of. There has to be an obvious explanation for this.

Belt slipping? Is the tensioner tight?

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Customer reply replied 2 months ago
Ok did some research on line it appears there should be a filter screen at the expansion valve in the liquid line and it's not there is that a screen or a metering device.

Should be just a screen, the expansion valve is the metering device. I saw that in the diagram earlier, but it's just there to catch contaminants.

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Customer reply replied 2 months ago
Nice

I know that's not helpful.

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Customer reply replied 2 months ago
Well just put another new Delphi compressor on vaccum now will see how this goes
Customer reply replied 2 months ago
Do you know what actuates that displacement valve is it suction pressure or what

I've been searching the service manual for a description of that, and can't find it, so I don't have an answer, unfortunately.

Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4,831
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Customer reply replied 2 months ago
All right your off the hook it was the new Delphi compressor was the problem.

yay!

lol

thank you, sir.

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