Installed new breaker. Motor hums and doesn't work

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  #41  
Old 03-17-06, 08:49 AM
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OK, that's fine. I have myself convinced that he has a capacitor start, with centrifical switch, since I myself have a 2hp compressor and the ratings on the label are virtually the same. Mine is a Doerr, however. If it gets to this, hopefully the end of the motor opposite the shaft exit is where the switch is located, mine is hard to see, the little springs are the giveaway. A wooden chopstick is one way of reaching in there, but you really ought to know what you are poking into...Lots of times, just exercising the switch is enough to get it going again; I might try some non flammable brake cleaner to remove dust and grime from that area. You don't want to wash out the bearing, though, which is right next to it
 
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  #42  
Old 03-17-06, 09:10 AM
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ok based on your own compressor if you think this one is similar than that is very possible. a cent. switch is not closed when the motor is energized it will hum draw excessive current and be in locked rotor state. also, failure of the cent. switch to open in a short time of the motor reaching 70-80% of its speed the start winding could be damaged. your probably right about the cent switch. a cap start ind. run motor when its considered an open motor with a belt connection will use the cent switch. a cap. start ind. run where hermetic for a/c equip. will use an amp relay. the open type cap. start ind. run is common for open type compressors with a belt connection. so now, the cap, the cent. switch, or a shot start winding?
 

Last edited by tach; 03-17-06 at 09:44 AM.
  #43  
Old 03-17-06, 05:49 PM
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tach wrote:
a shorted cap will show zero resistance. a good cap will deflect the meter then return to zero. a dvom will show ohms and then return to zero.
Actually a good cap will deflect towards a zero reading and then rise in resistance indication. Analog or DVOM. How quickly it rises is a function of the capacitance. Motor start capacitors are large enough to see a noticeable rise - as opposed as to just jumping to infinite.
 
  #44  
Old 03-17-06, 07:42 PM
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thanks rodek01, you have been a great help to trying and solve the problem. by the way i did not read your whole post, was it important. i have tested my fair share of caps, i stand by what i posted. have you had a cap in your hands and tested it? a known good one and a known bad one?
 
  #45  
Old 03-17-06, 08:35 PM
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Just a THOUGHT, After 40 something posts I did not read them all (I'm bad)
Has anyone yet asked if the motor was good? After all It has been sitting for THREE (3) Years. Have we asked the person to "meg" the motor? Even though I have seen them meg right there has been a problem. With the sounds of this dilemma I don't think it will meg normal.

Where was it stored?
Has It been operating?
And when last?

I feel the first thing to do is check the integrity of the motor. Some times we seem to over anylize things, and over look the obvious. Again Just a thought.
 
  #46  
Old 03-17-06, 10:05 PM
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> Has anyone yet asked if the motor was good?
> After all It has been sitting for THREE (3) Years.

How likely is this to have caused a problem?

It hummed. What more do you need to know?


> Where was it stored?
> Has It been operating?
> And when last?

These questions were already asked and answered.

We need a hand spin start test.
 
  #47  
Old 03-19-06, 05:54 AM
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You've never heard a bad motor hum? and not operate?
 
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