Question about Air Tools & Compressors
I have a Sears air compressor model 921-153500. When it starts in only runs for a few seconds and stops. It does not trip a circuit breaker in my shop. I removed the cover to the pressure switch and pressed a black button that appears to be a reset button. It will then again start and stop after a few seconds. I just replaced the pressure regulator as it was leaking. Compressor ran fine for a few cycles after the regulator replacement before the problem described above began.
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Posted on Jan 02, 2017
are you using an extension cord? if so, plug the compressor into a wall socket, if it fires up fine then your extension cord is too long or not heavy enough - other problems could be a bad start capacitor, a loose connection in the pressure switch, or a bad switch
Posted on Aug 18, 2009
1)Let your unit pump up.
2)Turn it off.
3)Find the supply line from the pump to the tank.
4)Remove the supply line from the pump head.
5a)If you hear air coming from the tank you have a bad check valve.
5b)If you do not hear air coming from the tank, you have a leaky
Posted on Feb 02, 2009
I have worked on many makita compressors and have run-across this problem on a few of them. Your compressor has a check valve that is supposed to hold tank pressure after the switch reaches set pressure. There is an unloader valve built into the pressure switch that releases the pressure in the discharge hose after the unit shuts off. The unloader allows the compressor to restart with-out any pressure in the discharge line. If the brass check valve is leaking pressure back into the system, air will leak out of the unloader valve. Follow the discharge line to the tank and you will see the brass check valve. To test valve for fault, run the compressor till it builds around 80 psi and unplug the unit from the wall outlet. Remove the 1/4" hose connector from the check valve and check for air leaking out of the valve. If it is leaking you can order form www.toolpartsdirect.com. or call the makita 1-800 number. The price is about the same. Good Luck on your repair.
Posted on Mar 19, 2009
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
Posted on Jun 16, 2009
SOURCE: breaker relay tripping out
If the unloading valve trips , which i think is the safety valve that tells me the compressor is pumping up past its maximum allowed pressure. that black switch should be the overload switch. check the amps of the wires going to the motor while its running and then look at the name plate of the motor to see the maximum amount of amps that the motor is allowed to draw.
Posted on Jul 21, 2009
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