compressor problem


Old 01-01-05, 12:27 PM
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Unhappy compressor problem

I have a Craftsman 2hp 12 gallon 8cfm @40 psi air compressor. It is fairly old. When i go to turn it on i hear the motor trying to turn but it cant turn and jsut buzzes. I took the belt off and it worked ok. Adjusting the tension I eventually got it to run for about 2 minutes and now I am back where i started with the buzzing motor. Im thinking the motor is not going full strength? any suggestions are appreciated.
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Old 01-01-05, 02:13 PM
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I would bet on a problem with your compressor unit. If the motor won't turn it over, it may be seized. If it isn't an oil less compressor, you may get it going by ading some oil. If not, you're probably looking at a teardown and overhaul. If it sat idle for a long time, you probably have some significant rust buildup.

Get the model number from the nameplate and look on the Sears website for an owners manual (assuming you don't have it). The manual will give you exploded views of the compressor unit and part numbers.
Old 01-01-05, 02:43 PM
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Dave could be right in the the compressor could be the problem.
There are other possibilities as well.

If you have a belt this is likely an oil type piston compressor.
Not entirely revealing, of you turn the pulley of the compressor over by hand you may be able to feel any binding.

My thoughts are that the starting switch or capacitor could be gone in the motor or the cord and/or plug is bad.
It would be normal for a motor to turn if any of these parts were gone while the belt was not connected.

Unless you wish to begin taking the motor apart you may be able to take the motor to a motor shop to be checked.
Be aware though that the prices of compressors have come down a lot in recent years and this may be an opportunity to replace it with a new one.
Old 01-01-05, 02:55 PM
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well Im borrowing it from a friend for the winter. I got one for xmas but it hasnt shipped yet. I should start by finding out if it requires oil. I know nothing about it except how to turn it on and drain it. I opened the motor earlier and nothing looked wrong. And Im not sure if I made it clear but when the belt was taken off the motor was power pinning not just turning by my hand. Like it usually does. I will look into the compressor. It is possibly to turn by hand but gives a lot of resistance. Is this usual? Thanks
Old 01-01-05, 05:19 PM
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im going to change the oil. I was just notified it hasnt been changed in 10 years...would that cause the problem?
Old 01-01-05, 05:32 PM
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If the compressor was having a hard time turning due to a lack of oil, adding oil will not help for long if at all.
The reason it will be difficult to turn in this case would be because the bearings have overheated and been damaged.

What I was trying to get across before is that it is possible for a bad motor to spin while not connected to anything and still be bad.

The compressor wouldn''t turn that easily if the belt is taken off.
You would need to feel how difficult it is to turn one that you know is good to be able to compare.

Also, if you took the motor apart to check it, you would have to have checked the start windings, starting switch and start capacitor with a meter.

Kinda sounds like the motor but you need to rule out the compressor.
Old 01-01-05, 05:51 PM
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the oil was black..but i am starting to get frustrated..i know where yu are coming from but i just dont know enough about this..
Old 01-02-05, 08:22 AM
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I used to have this same problem with my small compressor. It would start up fine with no load but then when it would try to restart under load it would just hum and sometimes trip the breaker. I found that the cause was from using to small of and extension cord. I went with a 12/2 cord and the problem was solved. I've now got a longer hose and use a dedicated outlet eliminating the extention cord all together.

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