8 Reasons Why Your Air Compressor Won’t Stop Running (And How to Fix it)

Most air compressors aren’t designed for continuous running, and the ones that are you probably won’t have in your garage, as they’re designed for industrial use. So if you find that your air compressor won’t stop running, it’s a sign that something’s wrong with it. There are a number of reasons for this, which we’ll cover in this article. So read on to find out why your air compressor won’t stop running — and how to fix it. 

1. A Problem with the Pressure Switch

An issue with the pressure switch can be a dangerous problem. The pressure switch tells the compressor when it has reached the pressure cut-off point, turning the motor off and ceasing to compress any more air until the pressure falls to the cut-on point. 

So if the pressure switch fails, your compressor will continue running and building pressure until the pressure release valve (PRV) is triggered and the valve vents air, lowering the pressure again. 

However, this won’t keep the compressor from running, and it can run itself into the ground if you let it keep going. 

If the PRV and the pressure switch fail, it could cause the compressor to rupture, which can cause serious injury or death. Luckily, the chances of both components failing are low. 

How to Fix a Pressure Switch

If your compressor is running past the normal cut-off point, make sure you don’t use it until you fix it. And the way to fix it is to replace the pressure switch. Unfortunately, it’s hard to find factory parts for air compressors. Luckily, you can use a different pressure switch, so long as the following factors are met:

  • The new switch fits the mounting on your compressor
  • It has an internal unloader valve — or connects correctly with the existing unloader valve
  • Has the same pressure settings (both cut-in and cut-off) or has adjustable pressure settings
  • Features the same voltage range as the old switch.

Of course, if your compressor is still under warranty, you can have the company fix the problem for you, as using an off-brand compressor switch could void your warranty. 

2. Faulty Pressure Release Valve

I mentioned the pressure release valve (PRV) above in terms of it failing to vent air when the pressure builds up. But this isn’t the only problem that the PRV can have. In fact, if your air compressor keeps running, a faulty PRV can actually vent air before the max pressure shutoff is reached. 

So if the PRV is venting air when it’s not supposed to, your compressor could keep running and running, trying to make up for the air that’s escaping through the valve. 

How to Fix a Pressure Release Valve

Fixing a pressure release valve is pretty easy on most air compressors. All you have to do is find the replacement part for your model and trade it out for your old faulty one. Make sure to depressurize the tank first and work with the compressor off and unplugged. 

Here’s a good video on replacing the PRV:

3. Bad Tank Check Valve or Seal

An air compressor’s tank check valve sits between the pump and the tank. Its job is to prevent air from flowing out of the tank and back into the pump. Air should only be flowing one way: into the tank. 

But a faulty check valve can cause air to leak out of the tank, which will prevent your compressor from building pressure, which will keep it running continuously. 

Or, on occasion, it could be that the seal between the check valve and the tank is bad, causing the leak.

How to Fix a Bad Check Valve or Seal

It’s fairly easy to replace the check valve. Again, you’ll need to bleed the tank’s pressure and work on the compressor when it’s turned off and unplugged. Disconnect the pressure switch tube from the check valve and then disconnect the outlet tube as well. This will allow you to remove the check valve from the tank and replace it with your new one. 

If you think the seal was to blame, make sure there are no obstructions stuck in the threading of the tank, and consider using appropriate thread tape on when you install the new check valve. 

4. Worn Down Intake Valve

The intake valve is where the air compressor pulls in air to compress. It’s an essential part of the system, but it can wear down, eventually. If this happens, the air compressor will struggle to bring enough air in to build up adequate pressure for your job. 

This can cause the compressor to keep running without building pressure. Note that some compressors have more than one inlet valve. 

How to Fix a Worn Inlet Valve

Inlet valves are pretty easy to replace and readily available. Most owner’s manuals include instructions on replacing these valves. Check your manual for specifics on replacing your specific inlet valves. 

5. Leaky Gaskets

If your compressor runs continuously but doesn’t seem to build enough pressure to cut off, you could be experiencing a leaky gasket. Sometimes the compressor will build pressure up to a certain point (say 50 or 60 psi, for example) and then it will just keep running without building any more pressure. 

This could be a leak in a number of components, and it’s hard to tell if you have a leaky gasket just by looking at the compressor. You’ll generally have to take it apart to determine if this is the cause. 

How to Fix a Leaky Gasket

You’ll have to take apart the pump housing for this one, which will take some time. You’ll also need to make sure you have the right replacement gasket. If you’re not absolutely sure this is the cause, you could end up taking this apart for no reason. That’s why it’s good to consider these other possible causes before taking apart your pump. 

If you do decide to replace your head gasket, here’s a good video showing you how. 

6. Other Leaks

Leaks can sprout up in various places on an air compressor. Some of those places aren’t accessible without taking some components apart (like a head gasket), but some of them you can spot without taking the compressor apart. 

To test for leaks, mix up a solution of soap and water. You want it nice and sudsy, as this will help you locate any potential leaks. 

Use a paintbrush or a cloth to apply the soapy water around the various exterior components of the compressor while it’s on. If new bubbles form, you’ve located a leak! 

How to Fix Leaks on Your Air Compressor

Some leaks can be fixed by cleaning debris out of the connections and/or applying some plumber’s tape to the connection. Others may need to be addressed by replacing the leaking component. It really depends on the size and location of the leak. 

7. Seals and Rings

There are several other places where air can leak from your compressor, causing it to keep running. Seals and o-rings are both places where this is likely, as these parts can wear down over time. 

Unfortunately, determining if an internal seal or ring is leaking can be difficult. Really, this is more a process of elimination than anything else. However, you can use the soap-and-water method above to see if you have leaks around any exterior o-rings or connections. 

How to Fix Leaking Seals and Rings

Fixing a leaking seal or ring depends on the type of compressor and the location of the leak. For example, if your tube seal is leaking, it will involve taking the pump apart, replacing the seal, and then putting it back together. 

It’s also a good idea to replace any gaskets and other likely leak-causing components if you end up taking the pump apart. 

8. Other Less Likely Reasons

There are some other reasons that your compressor may continue to run, but they are less likely than the ones mentioned above. However, that doesn’t mean that you shouldn’t consider them if you’ve already checked for the other causes mentioned in this article. 

These less likely reasons include:

  • Dirt and debris buildup (replace your intake filter regularly to prevent this). Also replace any other filters according to manufacturer instructions.
  • Your pressure adjustment screw is set to a lower PSI than it should be. Check to make sure it’s at the appropriate level. 
  • Using an undersized extension cord (although this is more likely to overheat the motor). Avoid using extension cords with your compressor if possible. Instead, use a longer air hose. 

In Conclusion

Most of the time, if your compressor won’t stop running, it’s an issue with the pressure switch. However, there are other causes of this issue, and the only way to determine what’s causing it is to diagnose the issue with the tips above. Fixing some of these issues is pretty easy, while others will take some doing. 

If your compressor won’t stop running, refrain from using it until you can fix it. Continued use will likely damage the compressor and may even prevent a safety hazard. 

Thanks for reading this article. I hope this helps you figure out why your compressor won’t stop running!

Justin

Justin is a full-time blogger with a passion for anything DIY. When he's not hanging out with his wife and son, you can find him putting the finishing touches on yet another home project he's taken on. He's also the creator of AllAboutAirCompressors.com.