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Fan speed problem

Discussion in 'Electronic Repair' started by Wayne Tiffany, Jul 21, 2003.

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  1. I have a room fan that now has a problem (this is a fan with 3 speed
    switches and one cap.) When I turn it on, it will speed up for about 4
    seconds and then slow down to just barely running. My first thought was
    lubrication, so I addressed that. So then I suspected the capacitor - it's
    a 3mf cap and tested at 3.178. I also disconnected it and tried a new one -
    no change. Then I measured the resistance of the 3 windings. They are
    231.8 low, 192.6 med, 116.3 high. I also didn't find any shorted to the
    frame. The model is Aries CH-16SF, UL listed 49L2, distributed by Dollar
    General.

    I know that sometimes it's easier to buy a new one, but I'm baffled by what
    could have changed to produce these symptoms and would like to understand
    it. My best guess is that the windings shorted somewhere out in the middle,
    enough to destroy the magnetic field, but not enough to heat up enough to
    feel it. Any thoughts?

    WT
     
  2. I tried jumping directly to the winding leads after the switches - no
    difference. I didn't try a new cord, however, I think it would be quite
    unlikely to have a condition other than a break, in which case I would then
    see intermittent operation.

    WT
     
  3. Mike Berger

    Mike Berger Guest

    Have you tried Dollar General's tech support?
     
  4. Didn't know they had one - I can't imagine them supporting something like
    this.

    WT
     
  5. lcoe

    lcoe Guest

    a current meter would be useful, too hi=shorted winding, too low=bad
    connection/connector. does the motor act like it's drawing current,
    like w/hum? --Loren
     
  6. Good thought - I'll have to measure the current draw tonight. However, what
    I remember, is that it sounds and feels like not enough current. I don't
    remember a lot of hum, but something there that tells me it's trying to do
    something. What it really feels like is the cap is bad - current draw, but
    not in the correct phase. However, I tried that. I'll check tonight.

    WT
     
  7. Ian Stirling

    Ian Stirling Guest

    For AC circuits especially, a loudspeaker (in a completely fingerproof
    insulated box) in parallel with a .1 ohm resistor, in series with one
    of the wires may be of use.

    You can easily hear current changes, plus it's cheap.
     
  8. My lubrication method was to take out the rotor, clean any hard, gunky,
    messy, whatever from all of the surfaces, lube the bushing, spacer washers,
    and the rotor shaft. Then reassemble. So, yes, I got both ends. Good
    thought, though. I can spin it by hand and it spins very freely.

    I measured the current draw last night. Low-.30 amps, Med - .35 amps,
    High - .50 amps. Doesn't seem excessive and seems to be in line for the 3
    speeds. Still perplexing.

    WT
     
  9. t.hoehler

    t.hoehler Guest

    Just a guess, maybe the cap is breaking down, maybe opening up? You can pick
    up ceiling fan run caps at Home Depot cheap. Might throw a few bucks at it
    this way, see what happens. I once had an Akai tape machine whose capstan
    motor would slow down to almost nothing after a few minutes of running,
    turned out to be a bad motor cap.
    Let us know.
    Regards,
    Tom
     
  10. Tried that first - checked the old one and also a new one on it. Even tried
    changing the value to see what would happen. No change.

    WT
     
  11. lcoe

    lcoe Guest

    from your responses, it seems you have indeed given this a genuine effort.
    my only other remark is that i was skunked by a ceiling fan, older, and
    had to buy new. iirc, the problem was shaft wear/balance. in this case
    the symptom was slow speed _and_ noise. i didn't have a reason to believe
    the fan blades had been bent and decided the shaft wore enough to allow
    some lateral or axial play that set up the vibration which then slowed
    the fan. ymmv, this was 40yrs ago, on a fan that was 40 yrs old at that
    time. --Loren
     
  12. No noticeable shaft wear. I know what you mean as I also had a fan one time
    that the bearing turned in the housing until it got loose enough for the
    rotor to drag. Not here.

    This has been a perplexing one, and I think probably a dead end. However,
    it's an interesting thought challenge. I guess the last action before the
    trash is tear apart the windings, thereby destroying the motor, but maybe
    spotting something. You know the old adage - never throw away a machine
    without first taking it apart.

    WT
     
  13. lcoe

    lcoe Guest

    motors are a special case, wrt to repair by amateurs, even die-hards like
    you (and me). very careful and lengthy examination and testing never did
    show me what went wrong with an 89Ford Escort starter that "failed" while
    the unit sat idle for 2yrs.

    i took to the parts house and it was "dragging", pulling way to much
    juice. took it and the replacement home, new unit turns the engine
    just fine. disassembled, cleaned, lubed, metered for shorts/opens,
    re-installed, sameo-sameo. and it still pulled excess current on the
    tester when i took it back for a core refund. skunked again. --Loren
     
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