Air Compressor Problem

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  #1  
Old 05-25-04, 06:22 AM
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Air Compressor Problem

I was given a Sears electric air compressor - sorry, don't have the model number (I'm at work) - I would guess it's 5 gallon 2 1/2 horsepower, and it's about 10 years old. It came out of a golf shop, so it got some pretty good use.

It starts to come up to pressure just fine, but when it gets up around 60-70 psi it starts to bog down and speed up, bog down and speed up, at a little less than 1 cycle per second, like it wants to turn off, then changes its mind. Sometimes the cycles get so 'deep' that it blows the circuit breaker. Sometimes it comes up to 90 psi and shuts down with no problem. If it gets past 70, it seems happy on up to 90.

I'm thinking this isn't too big of a deal and should be repaired with a replacement part or two, but I don't want to throw myself at the mercy of the Sears parts counter. I'd like to go in knowing what to fix. Could this be some kind of regulator problem or something along those lines?

Thanks in advance. You guys have been a great help and blessing in the past.
 
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  #2  
Old 05-25-04, 02:07 PM
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ribtips,

The symptoms you describe lead me to a motor that is overloaded.

The first thing I would check is that the cord and plug is in good condition, that it hasn't been replaced with one that is too small and that it is plugged directly into a receptacle and not an extension cord.

The next thing is to check that the guage is reading correctly. If someone was reading a faulty guage and tried to adjust the pressure based on a bad reading, the motor would overload trying to pump at too high a pressure.
If you are not sure of the guage this would not be too expensive to replace.

Another possibility is that someone put a slightly bigger pulley on the motor to try to get more capacity out of it, again overloading it.

Finally it could be that the motor is worn out but would be the last possibility.

The proper way to check it out is with a known accurate guage on the tank and a clamp on ammeter.
You would compare the amp draw stated on the motor with the actual amps at the time the compressor has reached the 100 psi cut out pressure.
 
  #3  
Old 07-05-04, 05:25 PM
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I finally messed with it...

Your reply started me thinking, and it dawned on me that I should probably check the oil level. As a matter of fact, there are several maintenance tip decals on the side of the tank.

Anyway, although it didn't really look low, I added a little oil, and it runs fine now. You were right - it was overloading, but it was related to the oil level. I should probably change the oil pretty soon.

Thanks much.


[QUOTE=GregH]ribtips,

The symptoms you describe lead me to a motor that is overloaded.
 
  #4  
Old 07-05-04, 08:55 PM
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ribtips,

If the motor was being held back by overheated bearings the pump is not long for this world.
You may get some idea if this is so by draining the oil and collecting it in a clean container.
Run the compressor for at least fifteen minutes continuously to warm the oil and put any contamination that may be present in suspension.

Use 30 weight non-detergent motor oil. Oil labelled for air compressors is not necessary.
 
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