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  1. #1
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    Arrow PAG oil absorption questions



    How long can I allow PAG oil to stay "in the open" before it absorbs too much water?

    When I put a vacuum on the closed system will it pull entrained water out of the oil itself?

    Are there any "tricks of the trade" that I can use to minimize the oil's exposure to air and even the system's exposure to air?

    Is exposure to air (I'm in Houston and there is about 80% humidity on the average) that big of a deal if I am going to vacuum out the system for several hours?

    I am waiting for Hurricane Ike to hit and pondering buttoning up my 1995, 4 cyl, Toyota Camry’s AC system. My compressor died and, so far, I have removed the evaporator, drier, compressor and condenser and have thoroughly flushed out the evaporator and condenser. (I found no evidence of particle contamination. I knew that there were two types of oil in the system so I wanted to clean that out. I was surprised at how little oil drained out of the old compressor – less than 2 oz.)

    After reading several posts I was concerned just how quickly PAG oil absorbs water vapor. The new replacement compressor that I bought is supposed to be filled with 8oz of PAG oil. The tech that sold it to me suggested that I drain it all out to verify that I have that amount of oil advertised and then refill it. (Actually he suggested to put 6 oz back into the compressor and 1 oz to the evaporator and 1oz to the condenser since I have completely flushed everything and will install a new receiver/drier. The Camry manual says that the system takes a hair less than 8 oz.) All this sounds reasonable to me but I expect that the oil will be out of the compressor for a couple of hours and in the vented system for a while longer before I can get everything hooked up and can apply a vacuum to it.

    Thanks,
    OC



  2. #2
    Brian_UK's Avatar
    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: PAG oil absorption questions

    Hi OC,

    PAG oil is very hydroscopic so will absorb water very quickly.

    The oil should be the last thing to the added after your rebuild.

    For some oil tests, not sure how scientific but, have a look here for some graphical effects.

    http://www.autoacsystems.com/fasttrack/Oiltest.html

    You need to discard all of the oil in your system including the stuff in the compressor if it has been opened for any length of time.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

  3. #3
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    Re: PAG oil absorption questions

    I have not heard much about PAG in HVAC applications. All the R134a systems I have worked on use POE.

    Keep the seals on the compressor and filter drier until the very last moment. And vacuum and charge right after finishing the connections.
    "If Hannah was an air handler, I would be a condensing unit so I could open her TXV and pump my refrigerant through her coils." - a HVAC friend of mine

  4. #4
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    Re: PAG oil absorption questions

    have not heard much about PAG in HVAC applications
    He's working on his car.


    ((OT, Hmmm, where have I seen that (star882) user name before ?))
    Last edited by Will; 13-09-2008 at 04:42 PM.

  5. #5
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    Re: PAG oil absorption questions

    You can't pull moisture from PAG or POE oils with a vacuum like you can with the 'other' oils.

    About the only way is with desiccant/driers.

    Replace the oil.

  6. #6
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    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: PAG oil absorption questions

    Quote Originally Posted by Will View Post
    ((OT, Hmmm, where have I seen that (star882) user name before ?))
    Just about everywhere, don't Google unless you have plenty of time
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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