This is not a good situation for any air compressor owner.
If the compressor keeps running, it will normally keep pumping air into the air tank or air mains. Eventually, the pressure in the system will activate the pressure relief valve. The compressor may keep running, but now, the compressed air that is being generated is venting to atmosphere… we hope.
The device on an air compressor that controls the start and stop is the pressure switch.
It will have a low pressure cut in setting, where, when the pressure in the tank reaches that level, the pressure switch will trip, and power will flow to the motor to start it. The motor starts, and compressed air starts flowing into the tank.
When the pressure in the tank reaches the high pressure, cut out set point, the pressure switch trips again, and now power to the motor is cut off, and the motor stops.
If your motor on your compressor won’t stop, and the pressure keeps rising in the system beyond the normal cut out pressure level, it is a pretty safe bet that your pressure switch has malfunctioned.
This is a situation that you want to rectify sooner, rather than later. If the cut out pressure level on the pressure switch has failed, and if the PRV fails too, then catastrophe could be the result.
If you pressure switch isn’t working right, or if your compressor won’t shut of automatically at the normal cut out pressure level, please don’t use it again until you get the problem fixed.