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Clutchless AC compressor question

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  • Clutchless AC compressor question

    I am curious as to why when turning a clutchless variable displacement ac compressor by hand it does not produce suction/pressure? I can hear what sounds to be suction-like sounds when turning the shaft. After I took it apart the pistons still move a little bit in minimum displacement so it must be moving some volume, so I'm wondering why it doesn't build any pressure at all?

    I know there is a bleed hole from the crankcase to the suction chamber. When these compressors are running attached to the engine, they start off in minimum displacement and should be pumping a small amount of refrigerant to produce some suction and discharge pressure, otherwise, how would the crankcase pressure decrease to allow it to go in maximum displacement?


  • #2
    It's a variable displacement. You are not going to turn it by hand and get much or anything. No question you could and feel it on others in when if new did that to spin oil thru it many folks can't start off with a full charge have a few minutes or less to charge before it will blow up from lack up oil moving,
    MetroWest, Boston


    • #3
      I guess I need a more in depth look into how they work. I know when cooling isn't required the solenoid connects the high side to the crankcase to push the pistons up higher so it is not pumping much, but it would have to pump something when cooling is demanded as the solenoid would close the crankcase off to the high side and open it to the suction side so the pistons move to maximum displacement.

      So, I would think turning it by hand being the pistons are still moving a little I should feel suction on the intake port and some discharge in the outlet side, but this isnt the case. Maybe the amount is so minimal while turning by hand that the small amount pumped is going into the crankcase through the bleed hole and then into the suction side and it's recirculating??


      • #4
        Originally posted by chaosthyre
        I guess I need a more in depth look into how they work.
        yep, I would say you need to look closer in how they are built.