There are a number of reasons why an air compressor will not cut off. Many of those reasons are written about on various pages on this website, however this page focuses specifically on the reasons why, and adds a link back to the forum page if you would like to ask a question about why an air compressor will not cut off.
In order for the air compressor to cut off, it is necessary for the pressure switch to “see” sufficient pressure to trip the pressure switch to off. When the pressure switch is off, power cannot flow to the motor, and the compressor will stop.
Therefore, the first reason why an air compressor will not cut off is because the pressure switch is not “seeing” the correct cut off pressure setting.
There are a number of reasons why an air compressor air pressure will not reach the cut off setting of the pressure switch and those are covered on other pages linked from the troubleshooting page on this site, www.about–air–compressors.com.
Typically these reasons have to do with failure of the compressor pump valves, high pressure valves, or pump gaskets. These issues have to be rectified in order for the compressor pump to drive sufficient air into the tank or air mains to raise the pressure to the point where the pressure switch and trip to off.
Another Reason An Air Compressor Will Not Cut Off
Another reason why an air compressor will not cut off is that the pressure switch itself is not reacting to the correct pressure setting in the switch, the pressure switch does not switch to off, power continues to flow to the compressor motor, and the air compressor continues to run until the pressure in the system reaches the cracking pressure of the pressure relief valve.
This latter scenario is a dangerous one and an air compressor that continuously builds pressure past the point of pressure switch cut off, to the point where the pressure relief valve cracks open venting higher pressure, should not be used again until the problem is resolved.
Typically this problem relates to the pressure switch points, the springs inside the pressure switch, or the diaphragm that shifts according to system pressure to trip the pressure switch off.
While it is possible to rebuild pressure switches, and there are a number of pages on this website relating to that, I personally couldn’t be bothered taking the time to find parts and rebuild the pressure switch that can be purchased online for somewhere between $15 and $50 depending on the type being used.
However, if rebuilding the switch is of interest to you, visit the site map page and scroll down to the link that takes you to the page about rebuilding pressure switches.
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