Question about Hitachi EC12 Portable Electric 2hp Air Compressor, Oil Lubricated

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Hitachi EC12 Compressor- weird hum

5 year old compressor, light duty use, less than 200 hours.
Now unit builds pressure, gauge of right side building fast, the one on the left slowly. When it reaches a certain pressure say 120, the unit suddenly blows off a burst of air.
After the burst of air, a weird electrical humm is heard for about 10 seconds, which stops.

Any suggestions?

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The burst of air you hear as the compressor shuts off is the cylinder unloading so it will not have to restart against a high pressure load. If the unloader is electrical it would explain the hum that you hear. This could be a normal function.

Posted on Sep 09, 2008

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