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Trifive on Facebook Admin
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Discussion Starter · #1 ·
My 2 year old air compressor motor just hums when I turn it on. I checked and everything turns free. any ideas?:confused0006:
thanks
 

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I had the

same problems w/ the junk compressor I bought @ Lowes.
The start capacitor could be blown....
Could also be running on 1 leg of the 240..[120V]
Take the cover off where the power cable goes in, and look to see if 1 of the wires is burned off...
The best bet is to do the repair, and install a start relay instead of dealing w/ the hi current draw going thru the pressure switch..
 

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Trifive on Facebook Admin
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Discussion Starter · #5 ·
I just checked the connections, they appear good. no burn marks or any scorching at the switch or motor.
 

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Assuming you can turn the compressor and motor over by hand okay, you've probably got one of three problems; the start capacitor is bad, the start winding has failed in the motor, or the centrifugal start mechanism or contacts in the motor have a problem.

Hope this helps.
 

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1 more item to check..The pressure check valve in the top of the tank. If it's stuck shut, theres air pressure backed up to the compressor, and the motor likely does not have enuf torque to start....
 

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Discussion Starter · #10 ·
turns free, the reset button worksand the relief valve works. I drained all the air out. No pressure built up. I'll double check the breaker.
 

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bought a new starter switch. we'll see if that's it.
Dave, I'm doubtful that the starter switch will fix it. On most modern 240 vac compressors, the starter switch is just that, a 2 pole switch. If your motor is humming, then it's probably getting 240 vac to the motor.

I think you'll find the problem somewhere in the starting circuit for the motor as per my earlier post.

Good luck!
 

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Discussion Starter · #14 ·
well the starter switch wasn't it. It looks like I'll have to take the motor off and have it checked. What a pain it's turning out to be.
 

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Discussion Starter · #16 ·
Not to familiar with electric motors. are the capacitors on the outside of the housing? which one is which if so?
 

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Trifive Automotive Electrical Wiring Expert
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Not to familiar with electric motors. are the capacitors on the outside of the housing? which one is which if so?
The capicitors are the round things on top of the motor. I can't tell which is the start capacitor. Take them both to an electric motor repair shop and they can test them and will have a replacement. There will be wires connected to the capicitors. MARK the location of the wires on the capicitor and which capacitor is which. There should be a size in Mfd. (microfarad) on each capicitor.
 
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