Pro-tip: How to adjust and set your air compressor pressure switch

The pressure switch is a small yet crucial component that can affect an air compressor’s performance and maintenance. It is responsible for regulating the amount of pressure in the tank to match the specific pressure requirement of your pneumatic tool. You can consider it an efficient safety feature that automatically shuts off your air compressor once the desired pressure is reached then turns it on again when the tank’s pressure drops and more air is needed.

Since the necessary air pressure varies according to the pneumatic tool you’re using, the pressure switch is a part that may often need adjusting and it works hand in hand with the air compressor regulator. Doing so will help you save on operating and energy expenses, prolong the lifespan of your air compressor and pneumatic tools, and prevent potential malfunctions or danger. Remember to always follow the manufacturer’s suggested tolerance limits.

Adjusting and setting your air compressor pressure switch may seem like a daunting task but it may not be as complicated or time-consuming as you think. We’ve prepared a list of tools and a step-by-step guide you can follow to safely change the pressure settings of your air compressor.

Identifying the Pressure Switch on your Air Compressor

The first thing you should know is what your pressure switch looks like and it could be slightly different for every air compressor type. In most cases, pressure switches have a compact rectangular housing that is approximately the size of your hand. Its housing could be plain and simple or contain a lever that can carry out “auto” functions.

Parts of a Pressure Switch:

  1. Terminals
    The terminals are where the incoming and outgoing wiring is located which modulates the pressure switch to either complete or break the circuit, signaling when the air compressor turns on/ off.
  2. Contacts
    Contacts are the two points within a pressure switch that split to interrupt a circuit and turn off the air compressor, or come together to complete the circuit and keep the air compressor running.
  3. Diaphragm
    Also referred to as the membrane, the diaphragm is a flexible piece of material that moves when the pressure within the air tank changes. The air presses up against this membrane as the pressure rises. As soon as the ideal pressure is achieved, the membrane pulls the conductive contact points apart to break the circuit.
  4. Relief valve
    This is a safety valve intended to relieve the pressure that is trapped between the check valve and the pump. It is located on the base of your pressure switch control and connected to the check valve by copper or nylon tubings. You can count on the relief valve to be triggered when the contact points separate. Understand that this is an air compressor part that is never to be tampered with unless replaced.
  5. Adjustment springs
    The spring is the component you adjust in the pressure switch to modify the cut-in and cut-out points for the air compressor. Tightening the spring will increase the pressure needed to be exerted on the diaphragm to drive contacts apart and break the circuit. Conversely, loosening the spring will reduce pressure.
  6. Auto/on/off lever
    You can find an auto/on or auto/ off lever in some pressure valves to control the pressure switch. When the lever is programmed to auto/ on function, the air compressor’s motor turns on and off according to the cut-in and cut-out settings. On the other hand, the auto/off function keeps the power to the engine disabled with a piece of plastic wedged between its contacts.

Types of Pressure Switches:

    • Fixed Range
      You’ll know you have a fixed ranged pressure switch when there is only one set screw or nut on the adjustment spring. This means that the differential range remains the same even after modifying the air pressure. For instance, increasing the cut-in pressure will instantly increase the cut-out pressure and vice versa.
    • Adjustable Range
      An adjustable range pressure switch will have two to three setscrews or nuts corresponding to the adjustment springs for cut-in pressure, cut-out pressure, and sometimes even for the differential range between the two points. Understandably, there is a greater degree of control here since you can make independent changes.

It is common to find the pressure switch and its housing mounted on top of the reservoir to allow the free flow of air from the tank to the switch. Plus, this way you’d easily be able to check the pressure switch and monitor how much pressure you’re using and determine issues as soon as you encounter them.

Because compressed air pushes equally in all directions and on all sides of the switch at once, the housing or the reservoir may be prone to damage and make it difficult to obtain accurate readings.

Tools Needed for the Job

The tools needed to adjust and set your pressure switch will greatly depend on the air compressor model you have.

Below is a general list of what you’ll need:
Safety goggles and gloves to protect your eyes and hands.
Screwdriver or wrench to access the housing and turn the adjustment screw or nut.
Dielectric/ tune-up grease/ or electrical solvent to make it easier to twist the setscrew/s.
*Stay away from flammable liquids especially when there are active electrical currents.
 Steel wool or sandpaper will be handy for removing rust from corroded contacts.
 Teflon tape is useful when you’re replacing gauges or piping.

A Guide to Adjust and Set the Pressure Switch

To save yourself unnecessary trouble, make sure you examine your pneumatic tools and determine the appropriate differential range before adjusting the air compressor pressure switch. It is important that you take note of the manufacturer’s recommended settings for both your pneumatic tools and air compressor.

  1. Turn off and unplug your air compressor
    To be absolutely safe, turn off and unplug your air compressor from its power source. Also, take the additional step of draining your pressure tank and look into the pressure valve.
  2. Locate the pressure switch and discern what type you have
    Once you’ve located your pressure switch, uncover its housing and discern whether you have a fixed or adjustable range.
  3. Adjust the cut-in pressure
    The cut-in pressure screw is usually the one nearest to the air compressor’s motor. Turning it clockwise will tighten the adjustment spring to increase pressure. Those who intend to decrease the pressure will then loosen the nut in a counterclockwise motion.
  4. Check the cut-in pressure
    Make sure the air compressor tank is empty by releasing the pressure relief valve and cap it when done. Plug the unit in and turn it on to check if the new cut-in pressure has been reflected. Observe the pressure valve to correct any issues if there are any. It is important that you turn off the air compressor before making additional tweaks to avoid electric shock.
  5. Set the cut-out pressure
    Ideally, the differential range between the cut-in and cut-out pressure should be set at a minimum of 20 PSI. It is recommended that the cut-out pressure is 20 to 40 PSI higher than the cut-in pressure. The mode of adjustment is the same, meaning a higher pressure is obtained from tightening the screw or nut clockwise while loosening it (counterclockwise) will yield a lower pressure.
  6. Inspect the cut-out pressure
    Turn on your air compressor and see if it successfully reaches the cut-out pressure point and shuts off. If it the air compressor runs past its cut-out pressure, the pressure relief valve may be activated instead. In any scenario, unplug the air compressor before it reaches a dangerous pressure level.

Troubleshooting Common Problems

On the off chance you notice any discrepancy in your pressure switch, immediately turn off and unplug your air compressor. Empty its tank and observe its pressure valve – you should see and hear the switch trip as the pressure drops lower than the cut-in pressure.

If the tank’s pressure is below the cut-in pressure, plug and run the air compressor then use a multimeter to check if the voltage is flowing from the pressure switch to the motor. If the air compressor doesn’t turn on when it tank’s pressure drops, your pressure switch is most likely broken.

Leakage is the most common problem pressure switches incur and it can be fixable after disassembly and reassembly. The places you can check for leaks are the electric wire ports, mounting components, and diaphragm.

Air leaking from the unloader valve or near the housing would usually indicate a crack or hole in the diaphragm. In this case, it might be better to procure a compressor switch replacement. You’d be wise to source parts from a reputable air compressor supplier in Singapore so you can consult trained technicians and secure a warranty.

When to adjust the pressure setting of air compressors

If you’re typically using the air compressor to power pneumatic tools with the same pressure requirement, you’d only really need to change the pressure settings when you replace an old pressure switch.

Lowering the pressure settings is generally okay for efficiency. However, you are advised to be cautious when increasing the pressure as it comes with the risk of damaging your pneumatic tools and air compressor, or worse triggering an explosion. Again, always follow the manufacturer’s recommended PSI.

What pressure should my air compressor be set at?

Almost any light to medium-duty air compressor can handle the 70 to 90 PSI range that the majority of air tools demand. To compensate for any pressure loss in the system, you should always set the compressor to supply more flow than is required. Therefore, the cut-in and cut-out pressures on your compressor should be set at around 100 to 130 PSI each.

As with any machine, air compressors need to be properly maintained to ensure their optimum performance. You should also be able to determine if all its components are functioning normally. Pay close attention to the air compressor pressure switch and be keen on adjusting it when the need arises. Also, be wary about changing the oil of your air compressor periodically unless you have an oil-free air compressor.

There are more than a few air compressor types including piston compressors and direct-drive air compressors. That said, the pressure switch may be slightly different per model. You are always reminded to err on the side of caution by following your manufacturer’s intended tolerance limit for PSI as stated in the user manual.