Air conditioning vac pump Q

Discussion in 'General Motoring' started by Randy G., Oct 7, 2009.

  1. Randy G.

    Randy G. Guest

    There is a WIDE range in price between the venturi style,
    air-compressor powered A/C vac pumps and the electric powered ones
    (like $30 compared to $150). Does anyone here have any experience
    using one of the "economy" venturi pumps with success? I don't mind
    buying good tools, but it would be nice to be able to save some $$ on
    one like this which will get very limited use.
    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Oct 7, 2009
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  2. Randy G.

    clay Guest

    Don't know from vacuum pumps but couldn't you rent one?
    clay, Oct 7, 2009
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  3. Randy G.

    James Sweet Guest

    The venturi type are not really very good.

    If you're comfortable lashing something together, this place usually has a selection of new
    surplus rotary compressors designed for window AC units. I paid less
    than 10 bucks for mine and another $2 for the capacitor it needed. I
    soldered a refrigeration fitting onto the inlet pipe and connect my
    manifold to that. Once it's all hooked up, I set it in a bucket with
    about 3" of water (well below the electrical terminals!) to keep it cool
    as there's no refrigerant flowing through it, then fire it up and let it
    run for about a half hour to pull a nice tight vacuum. It works very
    well, much better than even real vacuum pumps of the diaphragm type.
    Yeah, it's ghetto, but I've used it to service probably a dozen
    automotive AC systems and install several residential heat pump/AC units.

    You also could look on ebay, a couple years ago I picked up a nice
    (well, hideous when I got it) Welch Duo-Seal 2 stage vacuum pump for a
    buck. It looked like it had been dredged from the bottom of a lake, but
    a thorough cleaning, coat of paint, new oil seal and intake gasket,
    followed by a couple of days of running flushing oil and then a fresh
    oil change had it pumping down to under 2 microns. A new pump of that
    ability is pushing up on $2K. Even the most tired worn out abused rotary
    vane vacuum pump will work better than an air powered venturi. Heck, a
    modified bicycle tire pump probably would too.
    James Sweet, Oct 8, 2009
  4. Randy G.

    Randy G. Guest

    I did consider that, and it is still a possibility, but I have at
    least three cars to do (or would like to do) and maybe a fourth so
    thought having one on hand would/might save in the long run.
    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Oct 8, 2009
  5. Randy G.

    Randy G. Guest

    I thought so, but for the price I figured I would ask.
    Thanks for the link. I will check into that.
    I have no problem kludging something together if it will work.

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Oct 8, 2009
  6. Randy G.

    Tim.. Guest

    Don;t bother with the venturi ones, unless you have a VERY large compressor
    and like making alot of noise. They won't pull a good enough vaccum either
    really for a/c work.

    Motor driven type is the only way to go.

    Tim.., Oct 10, 2009
  7. Randy G.

    AS Guest

    Better vacuum pumps are capable of 40 microns of mercury or less.

    Not sure of the specs on the ones sold by Harbor Freight tools
    (, but they are cheap. For a regular vehicle 2.5
    CFM is more than adequate.

    Good vacuum importance can never be over emphasized. At least 1/2 hour
    after reaching max vacuum, 1 hour is better.

    Good luck
    AS, Oct 28, 2009
  8. Randy G.

    James Sweet Guest

    You won't get 40 microns without spending over $1,000 if buying new. I'd
    be shocked if anything from Harbor Freight even approached 1,000
    microns, but that said, I did the AC in my 740 years ago with a
    diaphragm type vacuum pump that didn't even come close to that level and
    it's been working fine ever since. You can never have too good a vacuum,
    but a lousy one won't necessarily make the job a failure.
    James Sweet, Oct 28, 2009
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