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

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Compressor runs great but pops off at 125 then bleeds down to 80 then tries to restart.i have changed high presure pop off.

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It souds like a sticky "non return valve". See the fix below.
The non return valve is the chrome part with a hex cap adjacent to the upper tank. Remove the cap and make sure the piston moves freely. Slight resistance is ok, but if it sticks your compressor willl continually blow off air.

The check valve or "non return valve", as listed in the Hitachi parts manual is definitely the culprit here, but there is an alternative solution to replacing the entire valve that was actually suggested to me by a Hitachi Tech when I stopped by my local service center to pick up a new non return valve. Obviously, the rubber piston swells and sticks to the point that the spring under the piston can't over come the friction. I removed the piston and carefully reduced its diameter, by hand, with varying grades of wet or dry paper and it now operates perfectly. If one is uncomfortable with such a repair, at least keep it in mind for a quick jobsite fix. I have now been running my repaired compressor for several months without issue.

Posted on Aug 23, 2010

  • mwsn Sep 29, 2010

    Could have saved some money if I read this fix first. Thanks

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September 3, 2010 reply: Your sandpaper solution worked perfectly. Thanks.

Posted on Sep 02, 2010

  • rick15 Sep 28, 2010

    This fixes the problem of blowing off or dumping air. It also solves the problem of the motor not starting or laboring. If this valve is working correctly, then the motor does not have to start against the high pressure in the tank.

    Thank you for the fix. It worked perfectly.

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It souds like a sticky "non return valve". See the fix below.
The non return valve is the chrome part with a hex cap adjacent to the upper tank. Remove the cap and make sure the piston moves freely. Slight resistance is ok, but if it sticks your compressor willl continually blow off air.

The check valve or "non return valve", as listed in the Hitachi parts manual is definitely the culprit here, but there is an alternative solution to replacing the entire valve that was actually suggested to me by a Hitachi Tech when I stopped by my local service center to pick up a new non return valve. Obviously, the rubber piston swells and sticks to the point that the spring under the piston can't over come the friction. I removed the piston and carefully reduced its diameter, by hand, with varying grades of wet or dry paper and it now operates perfectly. If one is uncomfortable with such a repair, at least keep it in mind for a quick jobsite fix. I have now been running my repaired compressor for several months without issue.

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