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Thread: Leak??

  1. #1

    Leak??

    pressurized a/c unit to 300 psi with nitrogen. it holds, but i can't get a good vacuum. I know the gauge and vacuum machine is good cause next unit vacuums good. ???

  2. #2
    Join Date
    Dec 2000
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    Could be moister, How long did you vacuum?
    Decide what you want, decide what you are willing to exchange for it. Establish your priorities and go to work." H.L. Hunt

    "In order that people may be happy in their work, these three things are needed: They must be fit for it. They must not do too much of it. And they must have a sense of success in it." John uskin

  3. #3
    Quote Originally Posted by dan wong View Post
    Could be moister, How long did you vacuum?
    Vacuumed for 1 hr or more, 300 psi shouldn't it be pissing if it can't hold a vacuum of -29. Two months later it's ice.

  4. #4
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    Yea, thats very strange. How long did it hold 300psi?
    Decide what you want, decide what you are willing to exchange for it. Establish your priorities and go to work." H.L. Hunt

    "In order that people may be happy in their work, these three things are needed: They must be fit for it. They must not do too much of it. And they must have a sense of success in it." John uskin

  5. #5
    Join Date
    Apr 2007
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    Pa,
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    Are you using a vacuum gauge and not reading by the manifold gauge. If the vacuum pump oil is virgin and the unit will not stay deep in a vacuum, there is probably a small leak somewhere in your connections or system. You could still hold a nitrogen charge in a system but not get down to a deep vacuum if there is sufficient moisture in the system or a pin hair type of leak.

  6. #6
    Join Date
    Nov 2006
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    Oregon
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    -29 inches is a whopping 25,000 microns. You're not even approaching the boiling off of moisture.

    Don't you have a micron gauge?

    I'd start by using a male to male connector at the hoses just to make sure it's not your setup. Once your setup will pull itself down to <500 microns then you can connect the hose to the service ports because you'll know the setup is OK.

    If you see the vacuum "stair step" it's way down from around 2000 microns to <500 microns then that's the boiling off of water vapor.

  7. #7
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    use a micron gage

    Gee, Davefr , you took the word out of mouth. I was going ask his micron reading. I normally tell my guys to vacuum to 400 microns.
    Decide what you want, decide what you are willing to exchange for it. Establish your priorities and go to work." H.L. Hunt

    "In order that people may be happy in their work, these three things are needed: They must be fit for it. They must not do too much of it. And they must have a sense of success in it." John uskin

  8. #8
    Join Date
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    If he is having trouble holding -29", a micron gauge isn't going to do him a heck of a lot of good.

    What he needs is a good electronic leak detector. My preference is an H-10.

    Put a trace of R-22 in, pump it up to about 150 with nitrogen and have at finding that leak.

    Once you are in the neighborhood, a good soap soution and patience is the answer.

    Once that is accomplished, then, and only then, will a micron gauge do him any good.

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