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  1. #1
    Join Date
    Jul 2018
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    Dewalt Air Compressor

    "First time caller long time listener" I have a small 6 gallon Dewalt air compressor for light home use. Upon the pressure switch closing it will speed up to the point where the start capacitor should drop out, Than slow to a hum. I checked the capacitor (checked OK) , bled all air so no chance of it starting under load. Bearings are good (took apart inspected, thing is under a year old and probably under a hour use). Pump spins fine by hand. Odd thing there is no potential relay or centrifugal switch, i thought there had to be??.Compressor will run sometimes. Capacitor is 120mfd 120 supply voltage. Thanks

  2. #2
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    Jul 2018
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    Thread Starter
    Could the 120mfd cap be used as a run capacitor? This is a plastic capacitor. I would expect it to blow up. The duty cycle is 5 minutes on this compressor.

  3. #3
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Take the motor to a repair shop or maybe better yet take the whole thing to the warranty rep as under a year it should still be warranted . . . until you mess with it.

  4. #4
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    Thread Starter
    Not overly concerned about fixing it. It was a cheap one from Farm and Fleet. More intrested in how its designed. Having a 120mfd cap witg no start relay or centrifugal switch. Was hoping for some insite. Maybe ill email our motor supply/repair shop we use.

  5. #5
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    Aug 2009
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    Hint: there is a switch built in.

  6. #6
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    Jul 2018
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    Thread Starter
    So its built into the windings?

  7. #7
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    Shot my motor repair/supply house a email. His response was they are using the 120mfd as a run capacitor. They get away with it because of the short run cycles. He stated thats how they do it in China lol. As far as it stalling out he told me to ditch the extension cord, had it running on a 25ft. 14g wouldn't think 25' would make a whole lot of difference but we will see.

  8. #8
    Join Date
    Dec 2012
    Location
    columbus, OH
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    Lol is the capacitor plastic or metal? Ive helped a friend mess with them but for the most part forget... actually i think we just got him by a couple of cycles bypassing the internal switch. But i did test the cap for him and that was good, i didnt know how it worked either.


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  9. #9
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    Jul 2018
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    Thread Starter
    Plastic

  10. #10
    Join Date
    Dec 2012
    Location
    columbus, OH
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    Quote Originally Posted by Spitz View Post
    Plastic
    Im thinking the switch cuts the start winding out completely. Its similar to older motors for furnaces that had a centrifugal switch and no capacitor at all but its made to run under really high torque(120cap and start winding) or putter along the rest of the time.

    Makes since it has two situations balls to tue wall or just refill.


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  11. #11
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    Thread Starter
    There is no switch or relay

  12. #12
    Join Date
    Dec 2012
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    columbus, OH
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    Yea there is


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  13. #13
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    Jul 2018
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    Wisconsin
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    Thread Starter
    The 120mfd cap is being used as the run cap

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