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-   -   Capacitor tolerance (https://www.askmehelpdesk.com/showthread.php?t=391052)

  • Aug 27, 2009, 12:07 PM
    Bill Mosley
    capacitor tolerance
    My harbor breeze celing fan is not working. All of parts of the fan (switch, reverse switch, etc.) all check out fine. This fan/motor has 3 caps in cased in a black sealed box. The values of the three caps are 3.5, 4 and another 4uf cap. The cap lists a +/- 5% tolerance and I measure 3.25, 3.65, and 3.7 respectively which is just outside of 5%. I don't feel the cap is bad but I don't find anything else wrong. The fan will not spin in any position, do not hear a hum; motor spins freely and I have verified power is getting to the motor. This fan has a light kit that does work. Any ideas?
  • Aug 27, 2009, 12:23 PM
    KISS

    Usually these go in Elect & lighting. Bad tolerance is usually a sign of a bad cap. You need to measure ESR to have a good test.

    Here are some diagrams of fans: Ceiling Fand wiring Diagrams

    www.ceiilingfanparts.com has parts.

    On the above site, note just how many switches there are.

    The reverse switch needs to be inspected.
  • Aug 27, 2009, 12:24 PM
    Bill Mosley
    Esr?
  • Aug 27, 2009, 12:31 PM
    Bill Mosley
    Effective series resistance, wouldn't I need a special meter to test this? Checking resistance with a fluke 189 won't tell me anything will it, even if I have a new cap to compare it to?
  • Aug 27, 2009, 12:37 PM
    KISS

    Nope. I would doubt that all 3 caps failed at the same time.

    ESR is like, you put the CAP in a circuit and apply a low amplitude sine wave and measure I and V across the capacitor. That value needs to be low.

    I don't susspect them. With a weak cap, you can sometimes spin the blades and it will keep running. It just is unable to start.
  • Aug 27, 2009, 03:47 PM
    Bill Mosley
    Any idea what the problem might be? I feel as though I have ruled out either switch, the cap, connection issue, or power problem. That pretty much on leaves the motor which has no visible problems.
  • Aug 27, 2009, 04:08 PM
    KISS

    The reversing switch is what I would suspect.

    If it's moved when the fan is running, bad things happen.

    You have 3 caps and I'm not sure how that integrates in except the speed switch selects cmbinations of capacitors.

    You basically have two windings, sometimes there are taps. Continuity will identify problems there.

    With 2 caps, they essentially selct the two in parallel for the highest speed and then the lowest cap and then the middle value. Speed switches generally select combinations of the caps unless it's a design that uses taps on the motor winding.

    You'll note that the reversing switch essentially reverses a winding. It's a DPDT switch with the ends crossed. Esesntially a polarity reverser when used for DC. That's why only 4 wires are used. They are either connected straight through or crossed.

    I still suspect that.

    Disconnect te cap.

    Test the motor winding - ohms.

    Remove the lamps and put ohmeter on power leads. Check for motor continuity through the swich positions. One should be infinate.
  • Aug 27, 2009, 04:43 PM
    Bill Mosley
    I tested the reverse switch and it is fine, I will ohm the motor windings. Thanks for your help, will let you know
  • Aug 27, 2009, 04:59 PM
    Bill Mosley
    One winding is 98 ohms and the other is infinite. It should not be infinite should it?
  • Aug 27, 2009, 05:33 PM
    KISS

    Nope. Might have to take things further apart.
  • Aug 27, 2009, 05:36 PM
    Bill Mosley

    It appears that one winding is shot but wouldn't it run with the reverse switch in the other position if all switches and cap are good? Might be better off replacing fan, at this point I already have a few hours into troubleshooting and with a new fan for $100 or so I think I might stop wasting time. I found a 10x135mm motor for $35 but the fan is 8 years old so the cap is probably close to failing also. Thanks for your help
  • Aug 27, 2009, 06:01 PM
    Bill Mosley
    Would the fan run in the opposite direction if the switches and cap is good? One winding for each direction right? Thanks again for your help

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