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Thread: Cooling Fan Melted?

  1. #11
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    Quote Originally Posted by rippin209 View Post
    Wouldn't the motor being physically stopped cause a electrical surge?
    I'm willing to bet that if the fan hadn't slipped the shaft, then the fuse would have blown before the wires melted. As noted, the fuse is sized to protect the electrical components. The mechanical connection between the motor shaft and the fan appears to be the weak point in the whole system (not surprising to me, the plastic fan is probably just pressed on to the shaft).
    In this case, the fan separated from the shaft before the motor rotor became blocked, though a blocked rotor would probably blow a fuse due to a current spike. As the purpose of the fuse is to protect the electrical components, and no electrical components were damaged, the fuse cannot be said to have failed/been oversized.

  2. #12
    Senior Member ST13Fred's Avatar
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    Glad you found/fixed the problem.

    There are 57 pages of very specific cable/harness routing on the various NC models to avoid interference.
    Even the handle bars have punch marks and are clocked at a specific position.
    If a tie wrap or hold down comes loose there will be trouble as everything is in close proximity to one another.

  3. #13
    Senior Member Cooling Fan Melted? Ruggybuggy's Avatar
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    I haven't had a chance to test a fuse size but will next week. I'll run an amp clamp around the wires when I lock the old motor and see what it will draw then will choose a fuse accordingly. Yes a fuse would protect the wires but a system designed to actually cause damage to the fan if it gets jammed is a poor design. I was luck that it didn't harm my rad. The melted fan had actually leftmarks in the rad.
    Last edited by Ruggybuggy; 5th August 2017 at 06:09.

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  4. #14
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    Running amperage is only 2.86 amps. Did not measure locked amps as I did not want to screw up my fan

  5. #15
    Senior Member Cooling Fan Melted? Ruggybuggy's Avatar
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    Well I did the test on a locked motor with different sizes of fuses. I went down to a 5amp and the fuse would not blow. Then I started to actually "think" and realized this wasn't going to work. Electric motors will draw the same current whether it's locked or not. The motor is turn by magnetism and amperage doesn't change because the armature is locked.
    Last edited by Ruggybuggy; 10th August 2017 at 04:05.

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  6. #16
    Super Moderator Cooling Fan Melted? 670cc's Avatar
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    Quote Originally Posted by Ruggybuggy View Post
    Well I did the test on a locked motor with different sizes of fuses. I went down to a 5amp and the fuse would not blow. Then I started to actually "think" and realized this wasn't going to work. Electric motors will draw the same current whether it's locked or not. The motor is turn by magnetism and amperage doesn't change because the armature is locked.
    I think the motor current does change based on whether the motor shaft is spinning or not. A stopped motor requires more current to get it running than it does once it's running. Measuring the current flow with an ammeter would be far more accurate than just trying different fuse sizes.

    Nonetheless, I think you've demonstrated that using exact fuse sizing to protect against this mechanical failure is rather futile.
    Last edited by 670cc; 10th August 2017 at 06:02.
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  7. #17
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    [QUOTE=Ruggybuggy;190768 Electric motors will draw the same current whether it's locked or not. The motor is turn by magnetism and amperage doesn't change because the armature is locked.[/QUOTE]

    Depends on the type of motor. The only way to verify current draw is with an amp meter.

  8. #18
    Senior Member Cooling Fan Melted? Ruggybuggy's Avatar
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    I would have assumed that the motor would be rather simple and would not have a "start up winding", if that's the correct terminology.

    “Never argue with stupid people, they will drag you down to their level and then beat you with experience.”


    ― Mark Twain

  9. #19
    Senior Member Cooling Fan Melted? dduelin's Avatar
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    The root cause for the fan failure was caused by (A) by not replacing the hose in the retainer or (B) the retainer failed. If the hose securely clipped back into the retainer after the fault was discovered then was it really the retainer that failed?

    A was self inflicted. B could be bad design of the retainer but if that is true and you still trust it after finding the hose loose than go back to A.
    Dave

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