What Does the Air Compressor Governor Do?

The difference between the air compressor in your garage and the air compressor in your car is that the one in your vehicle requires a governor. What exactly does the air compressor governor do?

Air compressor governors are responsible for regulating the air pressure needed to operate a car’s brakes. Typically, air compressor governors cut on at 75 PSI and cut off at 140 PSI. It should take about one minute for the governor to build about 30 PSI.

In this article, we will explore how an air compressor governor works, why it’s a critical component, and how to identify a problem.

What Is an Air Compressor Governor?

A car’s engine housing includes a compressor that provides enough pressurized air to activate the vehicle’s air brake system. These brakes are typically found in larger, heaving vehicles like trucks or buses.

Air compressors are controlled by governors, which monitor and regulate the input and output of air into the storage tank. If the pressure becomes too high, the governor stops pumping (cut-out phase), and if it is too low, it starts pumping again (cut-in phase). 

Air compressors are capable of compressing up to 495 PSI, which, when applied to brakes, can be dangerous to both the driver and the passengers.

How Does an Air Compressor Governor Work?

Air compressor governors are designed to work based on the specific vehicle’s system and its max and minimum PSI.

The average minimum pressure of an air brake system compressor is 75 PSI, while the average maximum is 140 PSI. Typically air compressor governors work within 30 PSI between minimum and maximum. Air compressor governors monitor and regulate the input and output of air based on this range.

How to Troubleshoot Air Compressor Governors

There are a few things to look for when inspecting an air compressor governor if you suspect there is a problem.

Here are two indicators that can help identify a malfunctioning air compressor governor:

  • Air Leaks

Leaks indicate a problem with the air tank diaphragm or the diaphragm’s seal. They won’t allow for the air compressor governor to cut off because the governor will have no ability to rebuild pressure. Air leaks can also be caused by incorrect installation during manufacturing.

To locate an air tank diaphragm hole, listen closely for a hissing sound under the hood as soon as you turn your car off. If you suspect a faulty seal- purchase a roll of thread seal tape for around $30. Re-tape the seal to prevent air from escaping. 

When replacing components of the air compressor system, check for any damaged seals before installing a completely new governor.

  • Overpressurization 

This one is a direct result of an air compressor governor malfunction.

If an air compressor governor isn’t regulating properly, it could cause an overpressurization of air in the tank. This is a dangerous issue that cannot be resolved by repairing any parts. A malfunctioning air compressor governor requires an entirely new replacement.

Replacement governors run about $75 apiece.

Why Is an Air Compressor Governor Important?

There are many reasons why air compressor governors are vital pieces of equipment in air brakes.

Here are a few:

Air compressor governors regulate the applied pressure for your vehicle’s brakes and protect the driver’s safety.

Air compressors provide the pressure to a car’s brakes, and the air compressor governor regulates that pressure. The bottom line is that if your governor isn’t doing its job, you may very well not be able to break and end up crashing your car.

Air compressor governors regulate the amount of air pressure released from the system.

Air compressor governors also help by regulating the amount of air pressure released from the system to maintain a constant flow of compressed air in the reservoir tank. Without a regulated supply, an eternally fluctuating amount of compressed air will be lost from the tank. Air compressors need to have consistent energy input and output in order to power machines properly.

Air compressor governors prevent damage to the air compressor itself.

Without an air compressor governor, not only will there be a lack of consistency in output, but you will also overwork your equipment. This can cause severe damage to your air compressor.

Air compressors have several parts, all of which must be functioning properly to prevent cracks in the system. Air compressor governors monitor and manage this system to keep it running smoothly.

If your governor is broken and the air is overpressurizing, you run the risk of damaging the entire compressor.

How Long Should It Take for an Air Compressor Governor to Build Air Pressure?

How quickly an air compressor governor builds air is a good indicator how well it is working.

Depending on the vehicle’s size and type, it should take one minute for the governor to build about 30 PSI. Air compressor governors should take about this same amount of time to release air as well.

For example, if your air compressor minimum is 80 PSI and it takes 5 minutes to reach 110 PSI, you have a problem on your hands and should consult a mechanic.

It’s a known fact that air pressure can fluctuate depending on the condition of the vehicle and the weather, so make sure to consider these factors. Air pressure will naturally increase as it gets warmer outside; thus, this situation is not something to worry about.

Air compressor governors are built to ensure that there is enough air pressure to maintain the brake system regardless of external factors.

How Do I Know If My Air Compressor Governor Is Bad?

To confirm that your air compressor governor has gone bad, be sure to get a professional opinion from a trained mechanic. However, there is an easy troubleshooting technique you can start with at home.

Follow these steps to test your air compressor governor:

  • Turn on your ignition, but do not start the car yet. Confirm that you are under 95 PSI by looking at the air pressure gauge. 
  • If you are over 95 PSI, pull your emergency brake.
  • Start your ignition.
  • Put your car into Neutral.
  • Start building air pressure by revving your engine to 1000 RPMs.
  • Look at the needle rising on your pressure gauge. Record the PSI when it stops rising.
  • As long as the needle stops before 140 PSI, your air compressor governor is functioning correctly.

For a better visual, check out this video detailing the governor cut-out test.

How Can Air Compressor Governor Mishaps Be Prevented?

You can prevent governors from malfunctioning through proper use and maintenance.

These simple maintenance practices can help:

  1. Clean out the air filter often– Air filters are responsible for keeping contaminants outside of the system. When dirt builds up within, it inhibits performance by restricting airflow. You should be cleaning your air filter roughly every 1-2 months, depending on how often you drive your car. Note that there are different kinds of filters, so be sure to purchase the correct one for your air brake system!


  2. Check air compressor air lines for blockages– Air lines are responsible for transferring air from the air compressor to your brakes. When these are blocked, it restricts performance which can damage the air compressor itself. It’s recommended that you inspect your air line once every six months.


  3. Do not overwork your air compressor governor by putting too much demand on your brakes– Overworking an air compressor will cause unnecessary wear and tear. Brake slowly and pay attention when you’re driving.


  4. Get your car serviced routinely– It’s essential to get all parts of your car inspected. Think of it as an ecosystem- if one part is lagging, another component could be suffering. If there’s a problem with your air compressor governor, it’s vital that a mechanic nips it in the bud before it causes any further damage.

The Conclusion

Air compressor governors are necessary for pumping air in and out of the air brake system in order to operate your vehicle’s brakes.

Typically, air compressor governors kick on at 75 PSI and kick off at 140 PSI. It should take about one minute for the governor to build about 30 PSI. If your brake pedal feels spongy or you start hearing a hissing sound from under the hood, it may be time to replace the air compressor governor!

A new air compressor governor will cost $75.

If you suspect other damage may be causing the governor to malfunction, check the air compressor lines first for blockages and clean out your air filter. Both of these are easy ways to keep your air brake system in tip-top shape.

Get routine maintenance done on your vehicle every 5,000 or 10,000 miles (depending on the make and model) to keep your air compressor governor working correctly.

      Residential & Commercial Air Compressors