Question about Dewalt 2 Hp 4 GAL Air Compressor

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Motor "bogs down" at roughly 120 psi...almost stops

Compressor will not reach the cutoff pressure of 200 psi. It geys to about 120 psi when the motor loads up and stops...I shut the switch before it does damage to the motor. I this a 2 stage pump that is somehow not working?

Compressor is 5+ years old with moderate homeowner use.

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You suspect this unit as being a two stage because of the unusually high cut off pressure. It is a single stage and the motor really has a difficult task and is being pushed to the limits. to reach this pressure. We usually reset the pressure to lower setting ~~ say around 140. Your pump probably has a leaking intank check valve (brass fitting at tank) or leaking valve plate in pump. Simple tests : with pressure in tank unplug compressor from outlet and listens for air leak around pressure switch. As you unplug the running compressor from outlet you should hear air leaking from pressure switch for just a moment as air is let out of airline from pump to tank. If air leaks out till zero pressure then change the valve. If tank holds pressure then valve probably ok. Next test, with no air in tank and air filter removed, plug in compressor and feel intake port for strong suction. If the valve plate is bad, suction will decrease as pressure neers the 120 mark till the point of feeling that air is actually blowing out of intake. With good valve plate there will be strong suction untill unit reaches set pressure. If valve plate is bad also change the cylinder and piston ring. Good luck with your repair.

Posted on Jul 29, 2010


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