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Re: compressor comes on and hums and goes off and does it...
The fact that your compressor completes a cycle indicates that the motor and pump are probably working correctly, however when the pressure switch cycles off there should be a slight release of the air that remains in the airline. If this air is not released thru the unloader of the pressure switch the motor cannot overcome the back-pressure in the airline and just hum. There should be a 1/4 in. hose extending from the pressure switch to the checkvalve in the tank. There is a small tab and needle valve that releases the air. Also check that the tank checkvalve is not leaking air back into the airline as this would cause back pressure. Finally, failing motor start capacitor will cause motor to hum. Weak capacitor will start motor when cold and no pressure in tank, but when things heat-up and with pressure in tank, motor may not have enough power to overcome load and hum. Enjoy
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This problem is caused by either the starter capacitor or the in-tank check valve. Ez to check. With no air in tank, start compressor; if motor hums or has difficulty suspect capacitor. If motor starts, partially fill tank and unplug the power. Check for air leaking at the pressure switch or air coming out of the air inlet (remove the air filter). If air leaking, replace check valve. If no air leaking, again let out all the from the tank and connect power. Allow the compressor to fill and shut-off. After the compressor fills, again listen for air leaking from the pressure switch unloader valve. If air continues to leak from unloader, replace the check valve. Good luck
You did not list model number, however if you have oilless type check the cylinder/piston by manually turning crank until piston is at top and examine cylinder for wear or scratches. If worn replace cylinder kit for full pressure. If ok check reed valves /valve plate for wear or broken reeds. If oil bath type, problem is usually air leak or reed valves / valve plate. As a general rule, you can keep track of wear by noting how many minutes it takes to fill the tank to cut-out. As the compressor wears it will take increasingly longer to fill. When new, and depending on tank size/ hp, most compessors fill within 2 ~ 5 min. Good luck
It sounds like the valve that releases the pressure out of the pipe that runs between the compressor and tank is not working once the tank is full and the motor automatically cuts off. This valve is attached to the Pressure control switch that switches the motor On & Off and usually has a small pipe going to it. You know the valve is working by the sound of a short spurt if air being released when the motor cuts off. If the valve is not releasing this air the compressor is trying to start under full load which the motor is not capable of doing, hence the humming and popping of breakers due to a current overload as the motor tries to start.
it sounds like your compressor is failing to start ... that usually means a bad starting capacitor ... if thats the case it will hum loudly for a few seconds periodically .. thats the compressor trying to start but it cant if the capacitor is bad .. it will stop humming when it gets too hot .. a thermal breaker will turn off the power until it cools back down .. dont let this continue since it will eventually damage the unit ... replace the capacitor .. the capacitor is usually mounted on or near the compressor .. it often has two sections .. one for the fan motor and one for the compressor ... since they are both in one case you have to change them both ,...
You stated that the compressor started up fine. I'll assume it reached it's max psi then cut out. Then upon reaching it's cut-in psi the motor ran slowly for a few seconds, then kicked off. I also assume you mean check valve when you refer to the non return valve. If this sounds about right then. The first thing I would do is bleed out all the air from both the tank and the pump supply line leading from the pump head to the tank's check valve. You can do this by simply loosening the fitting that attaches the line at the head or the check valve. Once done try running the compressor again. The purpose of this is to check the unloader valve. This valve bleeds off the pressure that remains in the compression cylinder and the supply line up to the check valve. When functioning normaly it will bleed off this pressure once the motor shuts off. If it is not working correctly then when your compressor starts back up (once it is already been filled) the piston will be working against a psi close to the max psi.
If the problem reoccurs only after the compressor has reached it's max psi, then the unloader valve is most likely the problem. If however it will not start up at all even after a complete bleed then it has to be something internal to the pump and\or motor.
Please try this and let me know (or repost) your findings. If it's the unloader valve I should be able to explain how to repair this valve. Good luck.
usally there is a releaf valve that takes the pressure off the compressor while it is resting. If that pressure is not off when the drive piston starts the motor will overload and blow the the breaker or reset. Check for a releaf valve for when the unit has reached full pressure