A/C compressor makes noise

Heating / Cooling / AC

  1. John Cailey

    John Cailey Crizila FABO Gold Member

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    I have a 74 Duster /6 with factory A/C. Running R134A. Compressor is known good. Running the correct pag oil and the correct amount of A/C charge. System blows cold air, but the compressor is very noisy ( snapping, chattering, especially at idle ). Sounds like it may be coming from the valve that sits in the compressor suction side port. I have no idea what this valve does or what it is called. Looks like it may be adjustable. When I replaced the compressor with a new reman, I just switched this valve over to the new compressor. Is this valve the problem and what is it - what does it do? Thanks, John
     
  2. Jim Kueneman

    Jim Kueneman FABO Gold Member FABO Gold Member

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    That valve should be removed if running R134a. It has the wrong pressures for R134a. It may freeze up unless you put a cycling switch. I just turn it off if I think it is freezing (rare in the dry Az desert air).
     
  3. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    Picture of the valve? York compressor ? What happened to the original compressor..what was reason for R&R? Was it R12 or previously converted to R134a.? Did you flush and evacuate system prior to assembly of current system ? and what other components did you replace? You say it blows cold but what are pressures and vent temps along with ambient temp. ?

    This will all be helpful info . I know of no valve at the compressor that will cause major if any noise unless you are talking about an isolation valve for repair / charging/ isolating compressor.

    What method did you use to charge ? Gauges hopefully or at least precise weight ?
     
  4. John Cailey

    John Cailey Crizila FABO Gold Member

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    Don't have a pic of the valve at this time. It sits inside the suction port side of a Chrysler RV2 compressor. I think its called a EPR valve. It works like a suction throttling valve on a Ford or a POA valve on a Chevy A/C system. This valve is needed in a non-cycling clutch system to prevent the expansion valve from freezing up - I think. Original compressor was marginal and in unknown condition ( this was a junkyard car purchase). New compressor was an exact replacement except set up for R134A. Yes, flushed the system. New expansion valve, accumulator / dryer, 6 oz. pag oil. Charged the system with 3 lbs of R134A. Tag on old compressor called for 3 lb, 6 oz of R12. Yes, used a R134A gauge set. High side at 210psi and low side around 30psi. with ambient around 96 degrees. Made sure the sight glass on the accumulator had no bubbles in it. Didn't do vent temp. It looks like this valve may be adjustable? I will take a pic when I blow the system to inspect this valve.
     
  5. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    EVAP PRESSURE REGULATOR valve ... Ok . There should be a screen on those made of nylon to protect compressor at the suc inlet from any debris in system . Was that visible with any restrictions or perhaps torn / degraded so basically open ? Although you seemed to have short charged it correctly ( ballpark anyway) to compensate for R134a operation in a designed R12 system ... With that your pressures seem to be within spec range .
    I mean I hate to condemn a compressor but they can operate properly( for awhile, depending on noise source) and make noise ... I've seen many many non mopar compressors do just that.
    The EPR in my experience is not going to cause noise unless it's severely starving compressor of refrigerant and oil coming in from EVAP. But you would see that drastic condition with your gauges .
    My money is on compressor ( reman , new , rebuilt I've seen them all defective as received but not overly much) but I'll be curious as to your findings when you further inspect.
     
  6. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    EPR valve EVAP PRESSURE REGULATOR . OK well was the nylon screen filter visible ? When u swapped? Although any restriction at this valve should show in temps and pressures . Looks like you short charged it properly to compensate for 134a , pressures look fine .(should correspond to about 38 degree CVT after preconditioning cabin out of sunlight and mix door adjust properly with those pressures but real world I'd say 40 to 45 degrees )
    I hate to tell ya it's likely a compressor , they can operate for various periods of time AND blow cold and correct pressures , I have seen plenty and have seen plenty of reman ,new , otherwise defect from rebuilder etc.
    I'll be curious as to what you find upon further inspect ... Spin that sob by hand also with open ports , how s it feel ?
     
  7. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    Sorry for double post
     
  8. John Cailey

    John Cailey Crizila FABO Gold Member

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    Thanks a lot for the input. Don't remember seeing a screen. I will run it again today and double check pressures before I blow it down and remove / reinspect the EPR. I'll take some pics. Spin the compressor by hand also - although I did this when I first installed it and it seemed to turn free. Could I run the compressor for a short with the system empty ( by-pass the low press. cut off switch ) just to see if it makes noise that way?
     
  9. John Cailey

    John Cailey Crizila FABO Gold Member

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    Ok, ran it for a bit this morning. Got a small leak by the low side port as the pressures were down from yesterday. 170psi on the high side and 26psi on the low side. Vent temp was 45 degrees. Ambient was about 82 degrees. See if I can upload the video of it running at idle. BTW, popping / snapping noise goes away at 1500 rpm and above. Everything seems to smooth out, including the pump belt.??? Can't upload video - "too large".
     
  10. John Cailey

    John Cailey Crizila FABO Gold Member

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  11. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    Unfortunately I don't have a yahoo account my friend. Video link immediately asks for login. You could run the compressor BRIEFLY with no charge since there is always oil in the compressor . But what will that determine ? If the noise goes away .... Ok ..there is no gas load on the compressor so that proves not much .. If it remains, you're at the same point in diagnosis .
    You could try this if you are so inclined .. Fully charged AC on at idle with noise present ... Quickly restrict discharge hose with large duckbills or soft jaw vise grips ( careful I mean quickly ) if noise really amps up or changes pitch dude it's your compressor ( I cannot stress quickly enough ) noise increase it will be immediate .
    You can also try recovering a half pound of refrigerant and use hot water to heat charge can of 134a then charge system while listening for noise at different Rpms... If noise is not present during charge you can almost be sure it's a starvation problem ( EPR ,txv, restriction) but your gauges do not indicate that at all and they will ,definitely . And u would not have 45 degree vent temp not even close.
    Did u find screen ? Any metal or black powdery clumps of soot ( Black Death) . The drier also is a filter and would be the likely place for debris to accumulate since it's on discharge side .

    Restrictions also almost always show up on gauges but I have seen on modern systems cases where pressures are not far off due to location of guage ports in which case infrared temp gun can find considerable temp differences on high side . They are usually extreme at the exact point of restrictions since that restriction acts like another expansion valve without temp modulation .
     
  12. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    Try another way to send vid , I'll pm u bro.
     
  13. John Cailey

    John Cailey Crizila FABO Gold Member

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    Ok, puled the EPR valve - pics attached. I have heard that they make an adjustable valve. Don't think this one is adjustable. At any rate, these valves are set from the factory at 26 psi for R12 operation. If I change over to R134A, the pressure should be lowered to 22psi.??? If the compressor was bad I would think the noise would be prevalent at all rpm's. BTW, this same noise occurred with the original compressor.

    EPR1.jpg

    EPR2.jpg

    EPR3.jpg
     
  14. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    I pm d you bro to send me the vid of this noise. Btw you said this compressor was built for 134a but you swapped a r12 EPR probably not the best idea but ... Hey if you think it's the EPR starving the compressor just run it without it and check bro. It's certainly not going to hurt anything to test .
     
  15. John Cailey

    John Cailey Crizila FABO Gold Member

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    I'll do that.
     
  16. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    And as I previously said I've seen compressors in my career that make noise at different speeds whether it be idle or higher Rpms . The methods I described previously will detect a low side starvation problem ... Gauges will show this along with temp readings along the suction pipe from EVAP to compressor .
    Also did you notice how quick your gauges equalize after shut down ?
    Did u notice any "pumping" or oscillating high side pressure especially when noise is present?
     
  17. John Cailey

    John Cailey Crizila FABO Gold Member

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    Both high and low side gauges run steady. I'll run it without the EPR valve tomorrow and see what happens. The reman compressor was supposed to be for R134A operation?- and it did not come with an EPR valve.
     
  18. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    Removing EPR Valves when Converting Your Mopar to 134a | Classic Auto Air - Air Conditioning & Heating for 70’s & Older Cars & Trucks. found this for you . Makes sense . havent heard your noise so I really don't know what you are chasing ,if it's light then perhaps this valve is cycling rapidly but I have nothing to go on if I can't hear it... Your post makes it sound pretty heavy so I was going that route .
    Anyway I'm sending u the link not so much for the noise , just remove it and check . But you will have to eliminate EPR in lieu of installing an AC thermostat at the EVAP to cut comp. operation at point of freezing EVAP. If not installed already .
     
  19. John Cailey

    John Cailey Crizila FABO Gold Member

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    I'll give classic air a call in the morning. Hey Man, thanks for all your help on this.
     
  20. 6pk2goDemon

    6pk2goDemon Mopar Mod Staff Member FABO Gold Member

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    If you upload your video to YouTube first & post the link it will work here...
     
  21. John Cailey

    John Cailey Crizila FABO Gold Member

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    Thanks, I'll remember that. I sent the video to his I-phone.
     
  22. John Cailey

    John Cailey Crizila FABO Gold Member

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  23. Caliscamp72

    Caliscamp72 Mostly sane GM Destroyer

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    No worries bro .
     
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