Have replaced the pressure switch, still the same

by Tom Kearns
(Newport RI USA)

Compressor will not shut off. Replaced pressure switch with new one ($75.00) and still wont' shut off automatically, when shut off manually and then flipped to auto it stays shut off untill pressure is low enough to turn back on, compressor runs to full pressure and then has to be turned off manually, so it works in one direction (turning itself on) but not turning itself off. Process reapeats. There are no leaks the compressor hold steady when not being used. Not sure what to do next.

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Bill says....

The device that turns the air compressor on and off is the pressure switch.

If your compressor reaches cut out pressure and it continues to run, power must be getting to the motor through the pressure switch. Therefore, the pressure switch has failed, has failed to switch at cut out pressure level, or has been wired improperly.

Use your multimeter to check the power line to the motor once the pressure reaches normal cut out. If power is still flowing to the motor, something is not right with your pressure switch.

Cheers,

Bill




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Have replaced the pressure switch, still the same

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May 27, 2011
 Pressure switch
by: Tom

Question, when a compressor states max pressure 150 psi but wont get above 140psi, could that be the problem with the pressure switch not reaching the required pressure to shut off? Or is the max pressure is what the compressor will do and the factory settings are 140, either way where is the pressure going once it reachs the 140 and why doesnt it build higher to reach blow off threshold?

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Visit the TROUBLESHOOTING page and read the info on the page linked from " won't build pressure ".
May 19, 2011
 Question regarding checking electrical
by: Anonymous

Have done a continuity check and all is good per the wiring diagram. What are the odds that I got sent a faulty switch. Also, I am curious how the switch reads the pressure to shut off, could there be somthing else that is sending the signal like the pressure itself that is not reaching the switch. Is the switch purely electrical, how does it read the pressure. Remember the switch is new. I also replaced this switch about 2 years ago with the same problem and it has worked fine until now. This is a Craftsman 6hp 30 gallon single cylinder oil free compressor. Please help

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Pressure switches usually have a diaphragm that reacts to the pressure in the system, and opening an closing points to stop or all electrical flow.

Since a new switch may be the least expensive solution, sure, try another one.

The thing is, if the power flows to the compressor motor with the switch trips on, and stops when the switch trips off, then the switch is likely not your problem.

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