Compressor Pressure Switch

What is a compressor pressure switch, and what does it do for us?

There are many questions about the operation of a compressor pressure switch on the pages of this site. As a result, there are a number of pages about compressor pressure switches, their problems, and the remedies.

These pages are about the operation of the pressure switch, and some basic troubleshooting techniques. See the other pages, linked from the site map page, for specific solutions to specific problems.

Pressure Switch Definition

A pressure switch is simply a device that reacts to the changing pressure in a system and either opens or closes a circuit to cause an action in response to the changing pressure in the system.

As it reacts to the pressure change in a compressed air system, the pressure switch either allows or drops an outgoing signal that is used to initiate an action.

In the case of our air compressor, the action is to turn on or turn off the electric motor of the air compressor.

Compressor Pressure Switch

compressor pressure switch

The photo above depicts a typical air compressor pressure switch on a DIY type of air compressor.

This black box contains the working components of the pressure switch, including the method of adjusting the cut in and cut out pressure levels of your air compressor.

The handle at the bottom front of the pressure switch with the red knob on the end is the OFF / RUN switch on this unit. Your compressor switch may vary, or you may not have a handle at all.

On the right in the photo you can see just the top of the tank air gauge on my compressor (with the white label on top ). This gauge shows the pressure in the tank and also shows the cut out pressure level reached when the pressure switch shuts off the compressor, and the cut in pressure level when the switch starts the air compressor.

If you wish to explore your compressor pressure switch, and I do recommend that you make yourself familiar with what is inside, make sure first that the compressor power supply is unplugged then go ahead, remove the cover. You want to be sure the power is off as there are live power connections inside the lid.

Under The Pressure Switch Cover

compressor pressure switch

The label under the lid on my pressure switch shows the electrical certifications, the manufacturer of this switch, and also some very important information for me if I have to replace the switch, and that is the cut in and cut out pressure levels for this switch.

Not shown on my photo, but also on a label under the cover, is an electrical schematic of the switch which you can refer to in the event you have pulled all the wires without marking them for re-wiring of the new switch.

I expect that your switch will likely have this information under the lid too.

More Under The Pressure Switch Lid

This next photo shows the wiring of my compressor pressure switch, and also the sealant-smeared adjustment nuts.
compressor pressure switch

There are two nuts buried in sealant, one on each side, and one of them is to adjust the high pressure cut out, and the other the low pressure cut in.

You will not normally need to try to adjust the pressure settings of your pressure switch. The settings are properly set at the factory for the correct operation of your air compressor, and there is little to be gained by messing with them. Unless, of course, you buy a replacement pressure switch for a burned out one, and have to set the proper cut in and cut out levels for your compressor.

You can see that the sealant on the adjustment nuts on my compressor is pristine, and it will stay that way. If I have a pressure switch problem, then I will simply replace the switch.

The cut out and cut in pressures levels of this air compressor are satisfactory for my needs, else, I would have purchased a compressor with higher or lower pressures.

Again, you do want to know what your present compressor pressure switch settings are. In the event you replace your pressure switch with an after-market unit, you may have to reset that new one to match the original settings.