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Thread: Puzzling Motor Problem

  1. #16
    Join Date
    Mar 2014
    Location
    Iowa USA
    Posts
    4,441
    Quote Originally Posted by Malcolm McLeod View Post
    ^+1

    Randy, this is a great place to apply 'law of halves' to trouble-shoot electrical problems. Test in the middle of a given system and determine which 'side' is bad. Test again in the ~ middle of that bad half and isolate the bad half of that half ...... repeat as necessary. The problem's possible location gets narrowed down quickly.

    Test when the motor won't start*:
    - If you have power at the output side of the controls (= approx middle?) , then the problem is in the last half of the system (wiring to the motor, or in the motor). First half is fine.
    - - If you measure the voltage at the motor and there is rated voltage, then the problem is in the motor. (All else is fine.)
    - - If you measure the voltage at the motor and there is no voltage, then the problem is in the wire between the starter & motor.
    - If you have no power at the output side of the controls, then the problem is in the first half of the system (power supply or starter). Second half may be fine, but is yet to be determined.

    ....repeat until you find the 'break' in the system.

    (I use 'half' loosely, pick convenient spots to test voltage that have accessible points (terminals, wire nuts, etc).
    ________
    * Please remove the belt and use good judgement when the controls/JBs/peckerhead are open!
    Problem is intermittent and he can not gain access to the motor connections when its installed.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  2. #17
    Join Date
    Feb 2017
    Location
    Northern Illinois
    Posts
    943
    Thanks for the suggestion, but I already did check them all. In fact, since I could turn the power off to the sub-panel, I just redid them all. The other thing is the jointer operated for 3 1/2 years with no problem on that circuit. While I realize things can change and I did check it to make sure, it seemed unlikely that the connections would be the problem. It's a 20 amp breaker with #12 wire run through conduit; no junction boxes anywhere, just continuous wire from the box to the outlet about 25 feet. Thanks again.

  3. #18
    Join Date
    Feb 2017
    Location
    Northern Illinois
    Posts
    943
    I appreciate all the help although that last few have been a little beyond my electrical capability and knowledge. I will definitely discuss with the service people when they come. I'm really fortunate in that this company is very good and knowledgeable with a lot of experience in the stationary power tool business. Either Jet vetted them, found them by accident, or they are one of the only companies in the area qualified. Anyway, your responses gave me some issues to discuss when they replace the motor because motor replacement at this point is a given whether it resolves the problem or not.

  4. #19
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298
    Quote Originally Posted by David L Morse View Post
    ...Using your tester to verify power at the motor in that cramped space and with a motor that could start up at any time is not something I would recommend.
    There is a safe way: turn off the power, connect the meter with a alligator clips or other gripping probes, then turn on the power. If needed, clip on and run several insulated lines out and tape the ends to the outside of the equipment, turn on the power and probe those lines.

    JKJ

  5. #20
    Quote Originally Posted by Bill George View Post
    Problem is intermittent (:: test when it wont start) and he can not gain access to the motor connections when its installed (:: where there's a will, there's a way) .
    .........

  6. #21
    Join Date
    Mar 2014
    Location
    Iowa USA
    Posts
    4,441
    Quote Originally Posted by Malcolm McLeod View Post
    .........where there's a will, there's a way) .
    That is easy to say, hard to do if you need to do it. He has experts coming, they will get it done.
    Last edited by Bill George; 11-21-2017 at 4:24 PM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  7. #22
    I can't help but wonder if the machine has some sort of thermal overload protection..... perhaps built into the motor itself. Does this motor have a time rating? Does this have a temp rating?

    Really, it does help to have a meter (VOM or DVM) along with some knowledge to narrow down the issue rather than assuming and unnecessarily replacing parts on the machine until the problem is resolved.

  8. #23
    Join Date
    Oct 2010
    Location
    Mountain City, TN
    Posts
    573
    Have you tried giving the motor a good smack when it doesn't start? Just wondering.

  9. #24
    Join Date
    Feb 2017
    Location
    Northern Illinois
    Posts
    943
    No, but it doesn't seem like that would be the best solution when Jet will replace the motor. A motor which requires a "good smack" is not the preferred motor.

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