Pressure Switch is a switch that acts to regulate pressure. It can be water pressure or air pressure. In all air compressors there is a pressure switch to act as a cut off when the air compressor has reached it’s desired working pressure. The switch does not look like a normal switch and to the eyes of a layman, they may will not know one when they see one. It is cylindrical in shape and most of the time there will be two electrical terminals and a threaded end so they can be tightly screwed on to the air compressor’s cylinder.
Basically this switch is always on a “normally close” state, which means it allows current to pass through between the two terminals. There are springs within the switch, which has been precisely calibrated to work at certain pressure. The tightness of the spring can be adjusted manually according to the user’s needs.
As mentioned, the pressure switch is always “closed” with the two terminals kept shut by the force of the spring. When the compressor is started, current passes through the two terminals allowing the motor to run. After running for a few minutes and pressured has been built up to the adjusted level, the spring is forced opened by the pressure an it cuts off electrical supply to the motor’s starter thereby stopping the air compressor instantly.
After using the air for sometime, the pressure naturally drops and once that happens, the pressure from the spring inside the pressure switch becomes stronger than the air pressure in the cylinder. This causes the spring to push the contacts of the two electrical terminals to the “close “position again, instantly starting the motor to build up the pressure once again.