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Why Does My Air Compressor Turn On and Off?

Sometimes, just when the world is dearest to you and you seem to be getting quite a bit of work done, your compressor randomly turns off on you. The opposite also happens, when you shut it down and it randomly turns itself on again. Why does this happen? Is this actually normal?

While we do not like it when this happens, this is a common occurrence called “short cycling.” It does not necessarily mean that something is broken or defective with your unit – but it does mean that you need to give it some of your attention.

What Cause Compressors to Shut Down?

Why Does My Air Compressor Turn On and OffCompressors are generally equipped with switches that have been given an oil temperature sensor as well. If the oil within the air compressor becomes too hot, then the sensor will catch it and the switch will send a signal directly to the on-off controller of your air compressor. This way, the system will be shut down and the unit will be prevented from incurring any damage due to high temperatures.

Issues that Might Cause the Compressor Shutting Down

If your compressor keeps tripping over, we know that it’s probably because the sensor is triggered by the high temperature – but what can cause this high temperature in the first place? Why does your unit keep shutting off after just a short cycle of use? Well, there may be plenty of reasons for that, some of them including the following:

  • There’s a leak somewhere
  • The ambient temperature is too high or too low, without proper ventilation
  • The oil levels are too low
  • You are using the wrong type of air compressor oil
  • The oil cooler is dirty
  • There’s an obstruction or dirt buildup in the oil lines
  • The thermostatic valve isn’t working
  • The airflow is restricted around the air to liquid cooler
  • The oil filter is plugged
  • The temperature switch is not working

Excessive temperature of the air compressor oils along with other issues can generally cause your air compressor to heat up, kicking your on-off controller into the defense system. If your unit keeps experiencing these kinds of short cycles, you might want to conduct some maintenance on the pats – and also ensure that you are only using the recommended air compressor oils.

Checking the Pressure Switch

To check whether the pressure switch is working or not, you may want to pull the cover on the switch and see what happens through the switch box as your compressor is cycling. However, you need to be very careful – after all, there are live terminals there.

Before you begin, make sure that your air compressor is shut off and that you have completely drained the tank. This will ensure that your air compressor switches on right away when you plug it in.

Once you plug in or start your air compressor, try looking at the insides of your pressure switch. Are you able to see the terminal points? Under normal circumstances, they should be moving when the switch trips on “on,” allowing the power to flow right through the motor circuit. If it all works well, then the issue is not with the switch.

Keep watching until the tank reaches its usual cutout. If you see that the points are opening and closing while the air compressor is turning on and off, you are most likely dealing with a faulty pressure switch. It’s probably caused by a diaphragm failure, which means you might have to fix or replace the switch. If you do not know how to do so yourself, then you may want to take your air compressor in the shop.

Checking the Power Supply

If you cannot see the pressure switch points (they are not visible in every unit), then you might want to go through another end and see if there is any power going through the wires. You may easily do this with a multi-meter.

Begin by probing the supply or line side of the pressure switch terminals, (specifically, where the wall plug feed terminates), and see whether it gets any power or not. If the compressor is cycling on and off, in the same style with the supply, then the problem is the supply. You either have a bad breaker or a connecting supply, or you have a broken supply line.

Using the Right Oil for Air Compressor

Using the Right Oil for Air CompressorIn most cases, your motor may get overly heated, causing the switch to turn your compressor on and off, simply because you are not using the right type of oil. Many people tend to use motor oil because it is the easiest-available one (you use it in your car as well, after all). However, motor oil also has detergents that make it unsuitable for air compressors.

Specifically, if you add motor oil in an air compressor, it will lead to carbon buildups that can cause your 12V unit or 24V unit to overheat. This will trigger the sensor that will signal the on/off pressure switch, leading to short cycles and your unit turning on and off automatically.

This is why you need to ensure that you are using the recommended air compressor oil. Granted, you may use motor oil that has no detergents, but at the same time, the investment would be quite the same. With specialized compressor oil, you will be sure that the device won’t get clogged.

Other Problems that Might Occur

If you checked the power supply, pressure switch, and compressor oil, determining that everything is OK, then your next stop is the motor run capacitor. In most cases, if the switch remains proper and the energy is passing through the motor circuit, then your start capacitor might be experiencing some issues. If the start capacitor is also ok, then the problem lies with the motor – in which case, you will certainly have to take it in the shop.

Final Thoughts

There are various reasons why your unit might be randomly turning on and off. However, if you can’t determine the cause after changing the oil, you might want to take it into the shop. They should help you determine and fix the issue.

About Jason Parker

Jason Parker learned that being a cyclist doesn’t only mean riding – he decided to build his own workshop for maintenance and fixing. Soon enough, he realized that there is no decent workshop without air tools (of various types). Through research, trial, and error, he decided to gather all his knowledge (so far) into these blogs and guides.

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