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Air Conditioner Fan Problem

Discussion in 'Electronic Repair' started by William R. Walsh, May 21, 2004.

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  1. Hello all...

    I trashpicked an 8,000 BTU Carrier air conditioner. It seems to be in decent
    shape apart from rotted out "accordion sides" on both ends. (Does anyone
    know where to get those alone?) However, the fan motor seems to have some
    kind of a problem. It will run fine for a while and then it will start
    dragging down until it stops turning altogether. However, giving it a push
    with my hand after it has stalled will get it moving again. Obviously I
    don't think it is safe to run this unit unattended.

    At no point does the motor seem to have actually siezed up, so I'm at a
    loss. I even took it apart, cleaned it off and oiled the bearings. Any
    thoughts? Best to put it back out on the street?

    William
     
  2. Seems a shame to put it out on the curb when the expensive part is still
    good (the compressor). How many wires to the motor?

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  3. Hi!
    That's what I thought and that's why I'm reluctant to do it. It's a 1989
    model and cools like brand new as long as the fan will stay running.

    It is a three speed fan and if memory serves there are four wires going to
    it.

    William
     
  4. jakdedert

    jakdedert Guest

    That makes sense...common, plus one wire for each speed. Does it exhibit
    the same symptoms on every speed? Perhaps it might run reliably on the
    highest speed? If so, then I'd run it that way (attended, of course) for a
    while and see....

    If not, a new fan 'might' be cheaper than an entire unit...you never know
    these days, though. OTOH, perhaps a motor shop--if any in your vicinity,
    there are in mine--might be able to help.

    jak
     
  5. Hi!
    Yes, the symptoms are present on every speed. The only difference
    (logically) is that the slower speeds become "gummed up" much more quickly
    than high speed.
    I had high hopes for this. It will run at least, but not always 20 minutes
    before slowing up and finally stopping with a hum from the motor.

    As mentioned, the motor starts right up with a flick of my hand and acts
    like nothing ever happened at all. However, power cycling the fan will not
    fix the problem unless it is off for a really long while.
    I found a single speed motor just a short while ago with the dual shafts...I
    didn't even know I had it. The shafts seem about the same as the original
    motor, but maybe they are a little smaller. The RPMs are within 100 of the
    original motor on high speed, so maybe I'll just rig it up that way and
    enjoy the unit until it dies of some other fault. I don't really need the
    lower speeds that much.

    More than anything else I'd love to know what the motor's problem is. I've
    seen a lot of motors die with reduced power or lowered RPMs, but this is the
    darndest thing...

    William
     
  6. Ken Weitzel

    Ken Weitzel Guest

    Hi...
    Missed the original post; and it's rolled off, so
    don't know the size of the unit. And of course
    don't know your home :)

    Anyway, just got to wondering. Big unit, 10 or 12k btu's?
    Older house wiring? Even aluminum perhaps?
    Possible that it's overtaxing the wiring, or even the
    line cord, heating it (increasing it's resistance)
    and pulling the line voltage down to a point that the
    fan would rather not run?

    Far fetched I know, but maybe worth asking. Better
    safe than sorry :)

    Take care.

    Ken
     
  7. ED

    ED Guest

    I would check the oil capacitor that should be tied to the motor. If
    it is changing value after the motor has been running the motor will
    experience a loss in its ability to produce torque and slow down.

    This is of couse assuming this is a L type motor.

    Ed
     
  8. jakdedert

    jakdedert Guest

    If it's not a lubrication problem, it would almost have to be a shorted or
    open pole...assuming an AC induction motor. If it's got brushes, then that
    would be the first place to look, but I don't think that most A/C motors fit
    that description(?). I've got some ideas, but I'm sure someone here has
    more experience with these than I....

    jak
     
  9. Hi!
    8,000 BTU. I haven't installed it yet. The home has central air, but it is
    not effective in all rooms. So you might say that I have a theory that
    involves placing said unit in a room that is under (or not at all) cooled.
    Older wiring, but that's slowly changing. Even the old stuff is copper and
    looks extremely good for its age. The old wiring never really had any
    problems per se (every problem we've had has been on the pole and not in the
    house) but things change and it is nice to have properly done grounded
    outlets or more outlets, and more breathing room for large appliances to
    run. I've also found a lot of improper additions to the old wiring.

    William
     
  10. Stan

    Stan Guest

    }Hello all...
    }
    }I trashpicked an 8,000 BTU Carrier air conditioner. It seems to be in decent
    }shape apart from rotted out "accordion sides" on both ends. (Does anyone
    }know where to get those alone?) However, the fan motor seems to have some
    }kind of a problem. It will run fine for a while and then it will start
    }dragging down until it stops turning altogether. However, giving it a push
    }with my hand after it has stalled will get it moving again. Obviously I
    }don't think it is safe to run this unit unattended.
    }
    }At no point does the motor seem to have actually siezed up, so I'm at a
    }loss.

    Have you tried spray component cooler to see if there is a thermal
    problem anywhere?

    Stan.
     
  11. t.hoehler

    t.hoehler Guest

    '
    Hi William, a friend of mine brought in his furnace blower motor a few weeks
    back, it was a four speed, perm split cap type motor that did exactly as
    yours is doing. Runs fine for about five mins, then slows to a crawl, give
    it a shove with your hand and it goes for about another five minutes. New
    cap did not help. Bearings were fine, no drag at all. It must be a winding
    breaking down, ruining the magnetic efficiency. I couln't smell any burning
    or see any damage - but a new motor was needed. We even tried running the
    new motor with the old cap just to make sure the cap wasn't bad - it ran
    fine with the old cap. We put it back together with the old cap and it is
    running fine. Some things are just not cut and dried - I too would like to
    know what happened to cause the motor to do this.
    Good luck,
    Tom
     
  12. I have seen this type of thing before, and don't have an easy answer.
    But there is hope.

    What happens if you tilt the entire unit, say 15 degrees to the rear,
    so gravity forces the fan armature to run toward the back of the
    shaft? This assumes there is some fore-aft play in the fan armature.
    Then repeat with the unit tilted 15 degrees toward the front. If
    there is a difference in performance, there is something still gumming
    up the armature shaft in the bearings. It is possible that when the
    fan armature is cool, it rotates freely in the bearing, but when the
    bearing heats up, something gets gummy and slows the fan down. If you
    find a difference in performance when the unit is tilted front and
    rear, it is time to take the motor apart and really clean the heck out
    of the bearings and their oiler supply. I would bet there are oiling
    tubes on the front and rear of the motor that feed oil to the bearings
    and that the tubes have ever been used, and are probably clogged with
    dust.

    At the very least, you have to take the motor out to put in a new one,
    and so you might as well see if you can get the present motor with
    multiple speeds to work. I am also assuming that the motor not only
    cools the compressor out the back, but also feeds the cooled air into
    the room, a dual shaft motor.

    Good luck, Bob Hofmann
     
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