How Does Air Compressor Pressure Switch Works? [All You Need To Know]

One of the most crucial parts of an air compressor is the pressure switch. We all know what it does. That’s all well and okay. But, what I’m sharing with you today is how does air compressor pressure switch works.

Most pressure switches feature a diaphragm that’s responsible for controlling the airflow. When enough pressure is filled inside the tank, the diaphragm deforms and stops flowing air. Likewise, when the pressure drops enough, the switch allows airflow again.

No matter why you are searching out to know how pressure switches work, let me quench your thirst by broadly elaborating. I’ve tried to cover all questions you might have regarding air compressor switch operation. Let’s get started.

What Is A Pressure Switch In The Air Compressor?

In simple terms, an air compressor pressure switch will measure the air pressure building inside the tank and turn off the machine when the desired level is achieved. Likewise, the switch will let the pressure build inside the tank whenever the pressure level drops.

You can control your air compressor by turning this pressure switch clockwise or anti-clockwise. The switch can turn your compressor on and, likewise, turn it off.

A pressure switch is used more frequently than other parts of your air compressor, which is why it’s essential that you take proper care of the pressure switch.

The switch also protects you from potential danger. How so? It prevents your air compressor from being over-pressurized and eventually exploding. So, you must ensure your pressure switch is working fine. 

Air Compressor Pressure Switch Works

How Does Air Compressor Pressure Switch Works?

Your compressor monitors the air pressure when it moves inside and outside the tank. The pressure switch is built in a way that it reacts when pressurized. Mostly, a diaphragm is responsible for responding to the pressure.

 When you turn your air compressor on, using the primary mechanism, the pressure inside the tank increases. When the tank’s pressure increases, it builds a backward pressure too. The backward pressure is known as cut-out pressure.

The cut-out pressure deforms the diaphragm in the switch deforms. After the tank has been filled with enough pressure, the diaphragm causes the switch to break contact, resulting in stopping the airflow.

By stopping the airflow, the switch ensures that your air compressor tank does not get over-pressurized. When the air pressure is constant at a particular volume, the diaphragm stays deformed.

Similarly, when the pressure inside the tanks drops too low, the diaphragm reverses back to its prior position and allows the motor to start again and increase the air pressure inside the tank. When the pressure inside the air compressor’s tank decreases, the pressure is called cut-in pressure.

Unless this pressure control process is interrupted by an outside force, the mechanism keeps going on. External influences include power disconnection, leaks, and other issues.

What Does An Air Compressor Pressure Switch Look Like?

Air Compressor Pressure SwitchYour air compressor pressure switch is far from being a regular switch. So, it’s apparent that it won’t look like a regular switch either. It often appears as rectangular housing. It can be plain or feature its own switch that will let you use several positions as ‘auto’ operate.

Usually, the reservoir accommodates the switch so that when the compressor is running, the air can freely flow inside the tank. Also, the switch monitors the airflow. You can quickly evaluate how much pressure you are using.

If your air compressor’s reservoir is damaged, the compressed air will simultaneously force the switch from every direction, creating a problem getting accurate readings.

Pressure Switch Components

The components of a pressure switch can differ from one air compressor to the other. However, a general air pressure switch will feature the following components.

  • Terminals

The wiring inside a pressure switch that completes or disconnects a circuit is connected through terminals. When the electric circuit completes, the compressor turns on and vice versa.

  • Contacts

Two points making or breaking the connection between themselves to complete and disconnect the circuit are called contacts. Conductive materials are used for making them.

  • Diaphragm

The diaphragm is also known as the membrane. It’s made of a flexible material that changes according to pressure levels inside the tanks.

  • Pressure switch relief valve

The relief valve is for relieving the pressure between the check valve and the pump. It resides on the base of the pressure switch

  • Adjustment springs

The spring is for adjusting cut-in and cut-out pressure. Tightening the spring will make the diaphragm need more air pressure to turn the compressor off. Loosening the spring will make the diaphragm need less air to move.

  • Auto/off lever

Some air compressor features auto on/off feature. You can control this setting using a lever or knob. If you set the lever to auto mood, the compressor will turn on and off depending on the cut-in and cut-out pressure you set before.

Air Compressor Pressure Switch Works

Testing An Air Compressor Pressure Switch

Testing your air compressor switch is easy. But you will need a different air source and an ohmmeter to run the test. If you don’t want to change your pressure switch anytime soon, I suggest you perform proper testing.

  • Unplug your air compressor from the power source.
  • Remove the housing by unscrewing it.
  • Make sure the wires between the terminal block and pressure switch are disconnected. You will notice brown or blue wires.
  • Ensure that you don’t disconnect the black and white wires. It can cause damage if you disconnect them because these wires power the pressure switch.
  • Find out where the valve is, and then apply air to the air compressor pressure switch. You will have to use more air pressure than your power switch is currently set to. Otherwise, the switch will not engage.
  • Make contact between the leads of the ohmmeter and the loose wires.
  • If your ohmmeter reading is 0, the switch closed because of the pressure. It’s an indication that the switch is working fine.
  • If your ohmmeter reads OL, open, or infinity, there’s a chance of an issue.
  • Adjust the set point of the pressure switch by turning the screw anti-clockwise. While doing it, pressure and look for your ohmmeter to read 0.
  • If your ohmmeter reads open even after disengaging the screw completely, you need to replace your pressure switch.

The process of checking the pressure switch can vary a little from one model to another, especially if you are using an industrial model.

Changing Pressure Settings

You can change your pressure setting using the adjustment sprint. If you compress the spring, the diaphragm will require more force in the tank to move. If you decompress the adjustment spring, the diaphragm requires less pressure.

There’s a long screw attached to the adjustment spring. The tension can be adjusted by turning this screw.

Turning the screw anti-clockwise makes the adjustment spring decompress that lowers the cut-out pressure. If you rotate it clockwise, the cut-out pressure raises by the spring decompression.

Leakage And Repair

The switch diaphragm can crack over time. In case this happens, air blows around and leaks from the tank. The air then moves the switch diaphragm and gets out of any of the switch housing openings.

If leakage happens, you will notice air coming out of areas like mounting elements, wire ports, etc. You may have to remove the switch cover to find the leakage.

If your switch’s unloader valve is placed outside the housing, you should look for leaks here at first.

If you are sure about the issue and know how to solve it, go for it. If you have any confusion about whether you should replace your switch or diaphragm, I’ll suggest you consult a professional before doing anything.


I can’t emphasize enough that how important it is to maintain the switch properly. Therefore, check the pressure switch parts regularly. To check, first, disconnecting the air compressor and check the switch for leaks.

The most common problem with leakage is at the switch diaphragm. Sometimes it may not show the correct air pressure reading. If so, you need to eliminate the leak. The best way is to change the diaphragm. You can find it at local stores or even online. If the switch becomes too damaged and goes beyond repair, the best solution is to replace it with a new one. But before you do, use some expert advice.

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Final Verdict

I hope you got everything on how does air compressor pressure switch works. Remember that safety always comes first. You should always be careful if you want to use your compressor without any unwanted accidents.

And keeping your pressure switch well and working is a part of keeping your air compressor safe. Even when you are turning your air compressor off, please don’t do it suddenly. The more delicately you use your machine, the longer it will last.

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