What Does The Compressor Pressure Switch Do?

Every air compressor that is designed to start and stop on it’s own has a pressure switch. So, what does the compressor pressure switch do?

Your air compressor has a pump. The pump is typically driven by an electric motor.

When the air compressor tank pressure falls – usually due to you using compressed air from the tank to accomplish some work – if the air compressor didn’t pump more air into the tank, then your available air pressure would drop continuously until… a) your air tool wouldn’t work any more b) there was no air left in the tank at all. Why doesn’t this happen? The pressure switch, that’s why!

Here is a photo of a variety of compressor pressure switches. Your air compressor pressure switch will look like, or somewhat like, one of these, we expect.

All photos: amazon.com
All photos: amazon.com


 What Does The Compressor Pressure Switch Do?

In the simplest of terms, the compressor pressure switch reacts to pressure in the compressor tank.

A power supply is wired to the switch. The other side of the switch is wired to the compressor motor.

As the tank pressure drops, eventually it will reach what is known as the cut in pressure setting of that pressure switch, the switch will trip to allow power through it, power then reaches the motor circuit, the motor starts, the pump starts, and a new supply of compressed air starts being driven into the compressor tank.

The pressure switch has a high pressure cut out setting, as well.

As the pressure in the tank rises, and the compressor pump continues pumping air into the compressor tank, eventually the tank pressure will reach the high pressure cut out level. At that point, the pressure switch trips to off, the power to the motor is cut off, and the motor and the pump stops.

Unless you have a leak in the system somewhere, the tank pressure will remain at the high pressure cut out pressure setting until you, once again, use compressed air.

When you start using compressed air again, the pressure in the tank begins to drop, and if you use enough air the tank pressure will reach the pressure switch cut in pressure setting, and the cycle repeats.

If your air compressor builds pressure past that pressure switches normal cut out pressure setting, it may be time to consider replacing your pressure switch.

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3 years ago

I have a NE-MA Mignon ( Torino) 39 Sentena. 5012713023141/ 02314.Pressure switch. Can you tell me how to wire it. I did wire it the same as the one I took off, but it blew the fuse. I changed the wires round and put the live to the bottom terminals and it still blew a fuse. I put the live wires to the top terminals and the neutral to the lower terminals. The motor did start then blew the fuse shortly after. Can you help me. My wire is Brown- Live. Blue- Neutral. Green-Earth.

4 years ago

I have replaced the pressure switch twice with two new paRts and My compressor Still keeps runnIng past the 150 psi untill it popps off at about 158, 160. Any other ideals?

David Thomas
7 years ago

The 1/4″ hose from pressure switch to tank is to short can I buy a longer one