Air compressor will not stop

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When an air compressor will not stop it could signal a problem with how the air compressor is pumping air into the compressor air tank.

Or, when an air compressor will not stop, it could also signal a major safety concern, and should be addressed immediately, before using the compressor again.

Compressor pumps up past cut out

If an air compressor runs, pumps air into the air tank, the tank pressure reaches the normal cut out pressure setting level, and the compressor continues to run and the pressure continues to build, this is a real problem! Eventually the PRV will let go, and the tank pressure should vent. The compressor will still run at this point though, and if it isn’t being monitored, it could run itself to death.

PRV doesn’t let go

The safety backup for the air compressor pressure switch is the PRV, the pressure relief valve.

The air compressor can pump air pressure into the tank to a level higher than the compressor is supposed to. If that pressure gets too high, there could be a major failure of a part, and if that compressor part is the tank, well, the results wouldn’t be good.

The PRV is factory set to a pressure higher than the cut out pressure of the pressure switch. If the pressure switch does not shut the compressor down at the normal cut out pressure setting, when the tank pressure reaches the PRV set point, the PRV opens and vents the air. If the PRV fails, my friend, you have a real serious problem!

If the compressor pumps air pressure past the normal cut out pressure setting, my advice is to not use the compressor until this is fixed.

Your compressor pressure switch should shut the compressor off

A typical pressure switch on your air compressor might be the Condor brand, similar to the one in the photo.

It is the compressor pressure switch that is supposed to shut the air compressor off when the tank pressure reaches the cut out pressure level. That pressure cut out level may be  in the 100 PSI through to 175 PSI level, depending on the brand and size of your air compressor.

The pressure switch reacts to the pressure in the tank and when that tank pressure reaches the cut out pressure setting the pressure switch trips to off, the power to the motor is cut, and the compressor stops. That is, if the pressure switch is working.

If the compressor continues to run past the cut out pressure setting then it is a pretty good bet that the pressure switch has failed. As far as I’m concerned, it is time for you to get a new compressor switch.

Replace the pressure switch

I know that finding after market parts for air compressors is hard, as so few of the stores that sell air compressors stock a comprehensive list of spares for the dozens of brands that they sell, and have sold, over the years.

When you are looking for a replacement pressure switch, as long as the replacement switch fits the mounting on your air compressor, if it connects properly to the existing unloader valve – or has an internal unloader valve – is the same voltage range as the existing and has the same cut in cut out pressure settings (or is adjustable) then you can use it.

It is not necessary to replace a pressure switch with exactly the same make and model. That is, unless your air compressor is under warranty. Using an off-brand part may void the warranty. But on the other hand, if the air compressor is under warranty, see the store where you bought it and give them the problem of replacing the switch. 🙂

That should take care of the case when an air compressor builds air pressure up past the cut out, and the compressor runs until the PRV lets go.

Air compressor will not stop – still

OK, there is another scenario where the air compressor will not stop and just keeps on running.

That is when the air compressor tank pressure will only pump up to a level that is below the pressure switch cut out setting.

That is to say, your air compressor starts OK – probably from an empty tank when you go to reuse it again, but instead of pumping up to the 100 – 175 PSI expected, the pressure in the tank only gets to 20 PSI, or 30 PSI or 80 PSI and levels out there. Even though the air compressor continues to run, the tank pressure refuses to increase.

Not correcting this problem can lead to self-destruction, or at the very least, overheating of your air compressor.

There are a number of reasons why this happens.

Failures on an air compressor that could cause this include:

  • intake valve failing
  • pressure valve failing
  • blown gasket inside pump
  • tank check valve is impeding flow
  • compressor leaks somewhere at the same rate that air is pumping into the tank

… to name just a few.

All of these will be discussed as a separate page linked under the Fixing Compressor Problems link.

More pages on this subject include:

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Tyler
Tyler
June 10, 2021 2:07 pm

My compressor pressure switch was replaced with a new pressure switch that is meant to cut off at 175, it keeps building pressure past 175, I also installed a 175 safety relief valve and that’s not opening either. What could be my problem?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Tyler
June 11, 2021 5:22 pm

Tyler, when the pressure bypasses the 175 PSI, is it showing that same reading on both air gauges?

Robert McDougal
Robert McDougal
March 20, 2021 10:38 pm

I have IR 2745N7.5 single phase that has suddenly begun running until the PRV pops off. Checked and replaced the pressure switch, no change. The compressor can also no longer be turned off by the switch on the magnetic starter, only by killing the power at the breaker. This leads me to believe the starter is stuck. Is there any way to fix this without buying a $400 replacement magnetic starter?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Robert McDougal
March 21, 2021 7:46 am

While I don’t from nothing about electric starters for compressors, I’ll be happy to post this here in the hopes that a kind I.R. compressor user will help.

Adam Pederson
Adam Pederson
September 7, 2020 7:47 pm

I have a 30 gallon air compressor that worked well for many years and recently it has continually run but only fills up to 50-60 pounds of pressure and then it seems to stop building pressure. The motor is still running continuously. Any recommendations on what the issue could be? It seems that it falls under the last category in the article on this page and just not sure what to try first.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Adam Pederson
September 8, 2020 10:54 am

Thanks for actually reading the page! 🙂 The compressor symptom you write about indicates that the pump itself is compromised. If air is bleeding out of the oil fill tube in significant quantity while the compressor is running, that points to piston seals/rings. If it’s that, it’s a pump tear down and rebuild kit required. Also, the same if it’s the valves or the gasket. So, if this were mine, I’d pull the pump apart, check the piston rings, and if not obviously compromised, I’d put in a gasket and valve kit if I could find one.

Gary
Gary
July 25, 2020 3:42 pm

I have an Industrial Air 30 Gallon tank that has worked flawlessly for ~15 years. Last month It started cycling endlessly. It is a 125 cut in and 155psi cut out switch. When it started cycling I noticed it was reaching ~177psi and the bleeder valve would open therefore cutting out motor operation until it reached ~144psi and close. Once closed the motor starts and of course reach ~177psi and the cycle continues (only allowed 2 cycles of that). I thought it was the pressure switch of course and ordered a replacement. Installed the new one and it did the same thing. Thinking it might also be bad I contacted the place I got it from they sent me another one and it did the same thing. So I abandoned that OEM part and purchased a cheaper Powermate part and have installed and does the same thing. I am thinking at this point it must be the Check Valve?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Gary
July 25, 2020 5:40 pm

Gary, if the power is crossing the switch to the motor when the compressor pressure switch calls for pressure, and the compressor runs until the PRV cracks open at over 175 PSI, and the pressure switch does not cut the power to the motor at the cut out setting, then it’s pretty much got to be a switch issue. What is the cut out pressure of the switch(s) you tried? Are you sure they are all set to cut out at 155 PSI or so?

That being the case, please double check the pressure switch wiring. Are you certain that the line (supply) is on one side of the switch and the load (motor) is on the other, so that the only way power can flow to the motor is if the switch has tripped and there is a completed path?

Gary
Gary
Reply to  Fix My Compressor Moderator
July 29, 2020 6:16 pm

Okay so with your comment I got to thinking that MAYBE the pressure adjustment on this Powermate wasn’t actually set for the rated pressures as indicated. On this one there is a pressure adjustment screw so I said what the heck. I turned it about 3-4 full turns and plugged in my compressor and what do you know! IT stopped around 155 psi! Sweet! The original and the other direct replacement OEM versions did not have a pressure adjustment screw as the power mate does. Thanks for the help and the direction.

Gary
Gary
Reply to  Fix My Compressor Moderator
July 29, 2020 1:45 pm

Well after 3 new PS installs I am hesitant to call it the switch although as far as my knowledge went that was the only thing that shut off the motor at the appropriate PSI. I have wired it according to the switch line in white, black, ground and motor white, black, motor ground is to frame already. White line in corresponds to Motor White (neutral) and black line in corresponds to black motor (HOT). Other than that I am really at my wits end on why the switches (all 125 cut in 155 cut out) never stop the motor. When the bleeder value opens within the PS the motor does in fact switch off however the pressure of course bleeds off.that being said I know that at least during that bleed off time the switch actually cuts power to the motor.

Tim
Tim
July 13, 2020 5:28 pm

I have a 15 year old version of this Kobalt 30 gallon compressor.

It has run flawlessly and I haven’t had to touch it (even stuff like top off the oil) until today. I was using an airscribe (6.3 SFCM) and the pressure went dry. It can easily keep up with the tool. So since the tank was still cycling I figured it just couldn’t keep up due to a leak. No leaks in the line so I went out to check and it was running constantly to try to keep up. So I thought I had a problem with the compressor. I went to turn it off and the switch doesn’t do anything, it keeps running. The only way to turn it off was to turn it off at the panel breaker. I shut off the air line with the regulator valve and turned it back on. Now it gets up to operating pressure which is listed at 155 psi on the tank and that’s what it usually shows on the gauge. It runs up to 155 and the relief valve blows but it doesn’t stop even with the switch. So I’m guessing there is something in the switch box that is causing this? I can’t even find the model on the online parts sites (the label says “098-3873” which if I just type in the number gets me one that was sold used. So if it’s just the switch box can you recommend a suitable replacement?

I do see one listing for the switch box for the current model, could this work?

PS if this helps I usually leave it on overnight if I’m working with air tools every day. Yes I know I shouldn’t do that but it might never kick or at most for under a minute every hour or so.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Tim
July 13, 2020 10:04 pm

If the pressure switch stayed tripped on, and the compressor motor was running, I don’t know why you would have run out of air, if the compressor could keep up demand with that air tool before.

If the compressor runs on past the cut out and the PRV cracks open, it’s certainly a switch problem too. I’m not sure that’s the only issue at this point. Yup, change the switch out and then check the operation, and do give us an update.

As to what switch, please see: https://fix-my-compressor.com/air-compressor-information/ . Scroll down to the Pressure Switch section and read the appropriate pages.

Tim
Tim
Reply to  Fix My Compressor Moderator
July 14, 2020 4:15 pm

Great thanks, I’m not sure why it did that either. Maybe it wanted to teach me a lesson. FYI these guys on Ebay seem to have one of everything, I ordered their Kobalt universal switch which looks almost exactly like mine.

PS do the air filters generally ever need replacing? They were a little dirty so I dunked them in soapy water. They look clean again. And I’m assuming that the dump valve is set to the max. tank pressure. Theirs doesn’t come with one. And your site is great, I wish I could get free help for my other machinery problems! Keep up the good work 🙂

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Tim
July 14, 2020 8:39 pm

Thanks for your kind comments. Replacing the filter element? Only if it’s degraded. Cleaning should do the trick.

The dump valve (PRV) that comes with it is set to crack open at the right pressure for that compressor. They are not all set to crack open at the same time. If you need to replace it, get one that cracks open at about 10-15 PSI higher than the cut out of the pressure switch upper setting.

Chewman
Chewman
July 7, 2020 11:19 am

Good Day! I have a Dewalt 30 gal air compressor. It will run up to pressure, shuts off fine in “auto” mode, but when it does, air is released from the tank via the switch {until it reaches the “on” pressure then starts again}. This also happens when I manually shut the motor off. I replaced the switch and the same issue persists. Any help please?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Chewman
July 7, 2020 8:43 pm

I hope you kept the old switch, as it likely was nothing to do with it. Check your tank check valve will you, and let us know what you find.

https://fix-my-compressor.com/air-continuously-leaks-out-of-the-unloader-valve/

Chewman
Chewman
Reply to  Fix My Compressor Moderator
September 6, 2020 5:41 pm

OK !!! So, here goes. I called Dewalt to get a check valve as suggested. After almost an hour “in que” I talked with a lady that checked and said they do not have that part in stock. I made SURE we were talking about the check valve NOT the pressure relief valve on the switch. She assured me we were both on the same page. She gave me the name and number of a company that would have the valve and I asked for the stock # so I knew I would be asking for the right part.

I called “Allparts” as suggested, talked with a pleasant enough gentleman, gave him the stock #, paid, got a confirmation, GREAT! This was a Thursday evening, the part came Monday!!! It was a pressure relief valve!!! SOB !!! I called back to Allparts and was connected to the same gentleman. Told him I got the wrong part, however it was the correct stock number FOR A RELIEF VALVE !!! He was not able to look up the correct # for the check valve.

Don’t want to call Dewalt again. Went online to Amazon.com to see what I could see. There it was, my check valve!!! Ordered it, took longer than I expected to be shipped. It came. Guess what? The fitting on the top of this thing is the wrong size !!!

So, back on the phone to Dewalt. This time I was put on hold again but, chose to attempt to use the “online chat” method while waiting. Almost instantly I was connected to someone {I hung up the phone at this point}. The rep said they do not handle the model I have, that there was another “division” that took care of this compressor.??? Your Dewalt but you don’t deal with this Dewalt product I asked??? Nope ! He gave me the contact info for that division.

Mat Industries, LLC, so I called them. A female answered the phone and I thought to myself {OK, so it was sexist to think that way, but hey the first lady from Dewalt didn’t do such a good job}. I told her my dilemma. She proceeded to make sure I was wanting the check valve, NOT the relief valve. Surprise, surprise, surprise! She asked how I knew it was the check valve. I told her, the little round plastic disk inside was sideways, I fixed that but it still wouldn’t work. She asked me how I “fixed” it, told her with a dental pick. She scolded me and said next time just soak it in warm soapy water, it should loosen it and that would fix the stuck valve. Yes Mame, I will.

Today I got the valve via UPS, tore open the package just knowing I got another relief valve. NOPE got the right part. Installed it, EVERYTHING is right in the world today!!!

Thanks for your help!!!

P.S.
The CORRECT stock # incase anyone else needs “E106002”

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Chewman
September 6, 2020 7:39 pm

🙂 Congrats on a job well done!

Derick Mayberry
Derick Mayberry
June 13, 2020 9:04 am

I have a central pneumatics 2hp compressor with the LEFOO Model LF10-4H DPST and I’m sure after reading all over this site I need a new one. Is there a quality product that will replace the LAFOO switch?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Derick Mayberry
June 13, 2020 9:55 am

Any brand of switch with the same characteristics will work. See this page and follow the links; https://fix-my-compressor.com/replacing-a-compressor-pressure-switch/

Derick Mayberry
Derick Mayberry
Reply to  Fix My Compressor Moderator
June 13, 2020 2:17 pm

Thanks for the reply but I was hoping someone with experience could give me advice on what brand would be best, what to get and what to stay away from I guess. I have mine hooked to a CNC and when the compressor doesn’t act right it causes all kinds of issues.
 
Thanks again.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Derick Mayberry
June 13, 2020 4:05 pm

That may yet happen, Derick. On the other hand, I’ve had Lefoo pressure switches on compressors for years with no problems. The pressure switch wears out, like any part, and the speed with which that happens is related to the cycles. You might look at FURNAS as an alternate, yet most, if not all, are made off shore any more. Good luck.

Dale Buchanan
Dale Buchanan
June 25, 2019 12:46 pm

Hello. I am having an issue with my Sealey Air compressor. Its a 50l 20hp oil free compressor and the issue I’m having is it just wants to continually run. I have so far replaced the piston ring, bore sleeve, gaskets and valves but the issue continues. It was ran for 8 mins today and I still had to manually shut it off. I’m not sure what pressure it gets to as it has a broken gauge but the tank took approx 30 seconds to empty after the 8 mins of running which I would imagine allows for a fair amount of pressure to have been built up. The repair is starting to get expensive so I was just wondering if there was anything that you would recommend I target next? Thanks

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Dale Buchanan
June 25, 2019 3:31 pm

Well Dale, first thing I’d do is replace that broken gauge. They aren’t that expensive and not knowing the pressure the compressor shuts off at is an issue.

Your Sealey must be an older version as it doesn’t appear as though they sell a 50 litre 20 HP air compressor today. Are you sure it’s a 20 HP and not a 2 HP unit?

Please provide the model number, and a photograph of the pressure switch from the side if you would, and we’ll check further. Make sure the tank drain is closed.

Don Curtis
Don Curtis
August 9, 2017 12:46 pm

I have an older Ingersol rand F11G compressor that runs untill the prv opens. It sat for a couple years. I’ve finally got it running but it wont stop pressurizing. I’m not sure what the prv looks like….

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Don Curtis
August 9, 2017 3:25 pm

Don, I couldn’t find a photo of the F11G so I’m not sure what the pressure switch looks like. I can say that typically, if an air compressor pressurizes air past the normal cut out pressure setting, that it’s the pressure switch that’s the problem. I would suspect a failed diaphragm if the pressure switch doesn’t shut off at normal cut out, or, welding of the points.

roy pitt-jones
roy pitt-jones
July 26, 2017 11:12 am

I have a Mark RF 5-10 RD screw compressor. It gets to 10 bar, as set on the danfoss controller, then the electrical valve opens and dumps the pressure back into the inlet filter housing. The compressor continues to run, with the valve open. It gets down to 8, as the differential is set to 2 on the danfoss, and the valve closes, and the pressure goes back to 10, and the whole process repeats. It never stops.
It is 10 yrs since this compressor was last used, and I do not remember it behaving this way. I’m sure it used to get to pressure and stop. Any ideas please?

Just to add…. in addition to the Danfoss controller, which is switching the electrical valve, there is a second, fixed, pressure switch switch. Which one of these is supposed to actually stop the compressor?

I will add some pics….

roy pitt-jones
roy pitt-jones
Reply to  roy pitt-jones
July 26, 2017 11:23 am

My compressor… ignore the knackered gauge. I have a new gauge hooked in out of view.

roy pitt-jones
roy pitt-jones
Reply to  roy pitt-jones
July 26, 2017 11:25 am

The Danfoss. This is working as when I set it to 8 (as pictured) it switched the valve open at 8 and closes at 6.

roy pitt-jones
roy pitt-jones
Reply to  roy pitt-jones
July 26, 2017 11:26 am

This is the electrical valve that switches ….

roy pitt-jones
roy pitt-jones
Reply to  roy pitt-jones
July 27, 2017 4:18 am

I think it’s just my memory that’s not working correctly. I now suspect this unit runs continually by design.

Russell Perkins
Russell Perkins
May 31, 2017 6:57 pm

I think I sent this before. I have a 6gal Bostitch air compressor it supposed to cut off at a150psi but it releases the air down to about 100psi and keeps running over and over what do I need to fix it?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Russell Perkins
June 1, 2017 8:38 am

Hey Russell, your post was moved to the Bostitch forum page and responded to there.

Bob
Bob
May 15, 2017 10:43 am

I have a Craftsman 5 gal, 125 psi compressor. Runs continuously, gets some air in the tank and the gauges don’t register anything. Any ideas?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Bob
May 15, 2017 2:24 pm

Bob, if the gauges don’t register anything, how are you finding out about the air in the tank. Are you saying that the compressor runs and runs and you get minimal pressure in the tank? If so, what have you checked, please?

Eric Richards
Eric Richards
April 21, 2017 12:55 pm

I own a WL651004AJ which is a Husky 17 gallon 5hp oil less compressor. I used your advice and replaced the pressure switch. The specs have it at 120psi turn on and a 150PSI cut off. After swapping it I turned on the compressor. The compressor ran for 15 minutes before I decided to run it off. The PSI would not reach above 95psi. I took off every connection and cleaned all the threads with a brush and wrapped new pipe tape on them and tightened them all back down.

What do I look for now or replace to get this compressor working again?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Eric Richards
April 23, 2017 2:32 pm

If the air pressure in the tank will not rise above a certain level, despite the compressor continuing to run, and there are no leaks, that suggest that there is a pump valve, gasket or piston ring problem. Have a look at: https://fix-my-compressor.com/when-an-air-compressor-runs-and-runs/ for things to look for.

Eric Richards
Eric Richards
Reply to  Eric Richards
April 21, 2017 11:59 pm

I found the supply line from the pump to the tank has a giant crack in it. I have ordered that part. I believe this will fix the issue.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Eric Richards
April 23, 2017 2:33 pm

That’ll do it, for sure! 🙂

Kenneth Broussard
Kenneth Broussard
March 20, 2017 1:05 am

My Dewalt air compressor d55146 will not build air pressure what could be wrong

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Kenneth Broussard
March 20, 2017 5:03 pm

What have you checked as per the list on this page, Kenneth? Is your compressor building pressure and blowing the PRV, is it running but not building pressure, what’s happening please?

John
John
January 30, 2017 8:23 am

I’m having a problem with a Porter Cable CPF 6020 compressor. It runs continuously and will not shut off. After scanning the questions and answers here I don’t see an obvious answer to my problem.

It will build pressure up to around to about 110 psi or a little higher. Once it reaches that pressure I can hear what sounds like air escaping from somewhere. It continues to run but doesn’t build additional pressure. If I shut the the compressor off no air leaks from anywhere and it maintains it’s 110-115 PSI pressure. If I turn it back on the motor stays off until some of the air in the tank is used. Once the pressure drops down to around 90 or so the motor restarts normally but then the cycle I just explained repeats itself. I have replaced the pressure switch with the a new OEM part and it didn’t help.

I’m not sure what to look for.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  John
January 31, 2017 10:56 am

Please tell me what the normal cut off pressure is for this compressor?

Peter Phillimore
Peter Phillimore
January 30, 2017 3:15 am

Hi i have just acquired an old air compressor, i have been told it works well but does not shut off just keeps going so you need to keep eye on it. I was wondering if you have seen anything like this one and advise how I can go about restoring it.attached photo.
thanks
pete

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Peter Phillimore
January 31, 2017 10:55 am

A venerable looking compressor, Peter. Hard to tell from the photo yet it looks like it’s got a pressure switch. If the air pressure continues to grow past the normal cut out, then it’s the pressure switch that’s likely at fault. If however, it runs and runs, but doesn’t build pressure much, those pages and what to do about these issues, can be found on the troubleshooting page on this site too.

tim buckwell
tim buckwell
September 2, 2016 10:46 am

my compressor will not cut out what is the correct pressure to enable my compressor to cut out

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  tim buckwell
September 2, 2016 11:43 am

Hi Tim. We note that you also posted to another page about this same issue. We have deleted the other posting. What have you checked on your compressor , as per the suggestions on this page, please? Not knowing the make or model of your compressor, we cannot tell you what the normal cut and cut out settings are. You can Google your make and model to likely find that info, and knowing that, can use that information to determine if it is your pressure switch that is the problem, or if you have other issues on the compressor.

Steve
Steve
September 1, 2016 2:32 pm

I bought a old heavy duty Sanborn compressor and the guy said it had a leak on the check valve which he assumed is the reason that it would pump up quickly to 100#-110# and not shut off but also not build any further.
The pin hole in the pic I assume is there for a reason. That is where the air is coming from while pumping.
When it is unplugged it will hold and maintain the tank pressure.
Would this be weak valve discs or rings?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Steve
September 2, 2016 10:15 am

The photo helped, Steve. Thanks. Yup, this hole is there to act as the unloader for this compressor. It does bleed air all the time the compressor is running, and also bleeds air after the compressor stops, until all of the air over the piston is gone. If your tank check valve is not seating properly, air in the tank will continue to bleed out of this hole until your compressor cuts in to refill the tank. That the hole is not bleeding air when the compressor is off indicates to us that the compressor tank check valve is fine. You need to look at the pages about why compressors runs and don’t build air pressure. They will help understand why your air compressor plateaus at a pressure level below cut out, and as a result, will run continuously until it overheats on thermal and shuts down.

Waqas
Waqas
August 17, 2016 9:45 am

hi
i have the same problem that i am facing with my FIAC new silver 10 screw compressor that motors continues to run even after it the tank pressure is reached to 10 bar. The compressors doesn’t builds any more pressure but the motor doesn’t stops i have checked the pressure switch it is okay i have replaced the switch as well. kindly help what could be the issue?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Waqas
August 18, 2016 12:10 pm

Please review your manual or contact FIAC to determine if this model of compressor is designed to have the motor run continuously, but for the compressing of air to unload when the cut out pressure is reached. Rotary screw compressors often run continuously, loading and unloading as the pressure in the system varies. Since your compressor does run continuously despite the replacement of the pressure switch, our guess is that the Silver 10 Encapsulated Screw Compressor is one of those designed to run continuously.

Ernie
Ernie
July 29, 2016 4:13 pm

Andrew i had the same problem,new switch but i let run and when it hit 160 psi it shut down,at 160 psi

Jon
Jon
July 22, 2016 3:22 pm

Hi there,

I’ve a Wolf Air OL 185. It continuously runs up to 100psi when the PRV kicks in, but carries on running until I shut it off.
If I use the air gun whilst it’s running at 100psi I get a quick blast of air but then the pressure dies down to nothing real quick. If I switch it off then exactly the same again – like it needs to build but then dies down again after a few blasts.
Sometimes after the pressure has built up and I turn it off manually, use the air gun again a couple of times and then go switch it on again to build the pressure back up, it doesn’t turn on at all?
Do I need a new switch ‘AND’ PRV, or should I just try the PRV first?

Many thanks in advance.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Jon
July 24, 2016 10:25 am

What is the normal cut out pressure setting for your Wolf Air OL 185? We take it that it’s higher than the pressure at which the PRV lets go? If so, the PRV itself may be damaged or failing. Sometimes it gets contaminated by oil from the compressor, and starts to release early. Try rinsing it in solvent, and when dry, reinstalling to to test.

As to a rapid drop in line pressure to your air gun, are you saying that there is plenty of air in the tank, but that, when you trigger the air gun, the supply to it drops too quickly? That suggests your air regulator has a problem.

As to the compressor turning back on issue, if you are not using an extension cord, and this is a relatively new issue, and if you hear nothing when the pressure in the tank drops below the normal cut in, that suggests either the pressure switch has failed, or something in the line to the motor circuit has failed, and that often points to the start capacitor. If you use a multi-meter to test the motor side of the pressure switch to see if there is power flowing through it when the tank pressure is below cut in, that will tell you whether or not the switch has tripped to ON, and if so, that suggests that the switch is fine, and it’s a power problem farther along the motor circuit.

edmon
edmon
May 25, 2016 10:17 am

I have triplex GA11C medical compressor with dryer.

The compressor motor will not stop even the unloading pressure cut in, and when the dryer purge the 3 compressor run together and I have a plant fault alarm.

I already increase and decrease the setting off cut in and cut out of pressure but still the compressor is still running.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  edmon
May 25, 2016 2:32 pm

We are not entirely sure what the compressor problem is, Edmon, and we cannot find detailed information about your GA11C compressor. Is it an Atlas Copco make?

If the air compressor tank reaches cut out pressure and the compressor motor fails to stop, then we would look with a multi-meter to determine if power was still flowing through the pressure switch even though the tank pressure had bypassed the cut out pressure setting. If so, that points to a failed pressure switch.

edmon
edmon
Reply to  Fix My Compressor Moderator
May 30, 2016 10:48 am

thankyou verymuch for your time and advice ….

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  edmon
May 30, 2016 11:49 am

🙂

Ally
Ally
December 8, 2015 10:59 am

Hi,
I have the same problem as above the motor keeps running until the PRV operates and the pressure switch does not stop the motor when it reaches the stated 8bar max pressure.
I purchased a replacement pressure switch from the manufaturer this did not fix it , the manufacturer sent a second pressure switch but this did not fix it either, the motor still does not cut out.
Could it be that the PRV is set too low and therefore operates before it has reached 8bar pressure instead of it’s stated 8.8bar pressure limit ?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Ally
December 8, 2015 1:47 pm

At what pressure is the PRV letting go? Watch the tank gauge, and note when the PRV cracks to release air.

Ally
Ally
Reply to  Fix My Compressor Moderator
December 8, 2015 4:26 pm

hi,
according to the gauge just over 8bar,.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Ally
December 8, 2015 5:01 pm

We don’t know the make of your air compressor Ally. If it’s a lower end, consumer model, the gauges used are not of the best quality, and may have a variance of 3-5+ PSI displayed different from the actual air pressure. If the compressor has a cut out of 8 bar, and the PRV cracks “just over 8 bar” then it is possible the PRV itself has failed. If yours has the ring in the end, when the tank pressure gets to the point where the PRV lets go, push in on the ring to hold the PRV shut, and let the compressor run until the tank pressure increases 1/2 a bar or so. It is possible that the tank pressure is not getting to the pressure switch cut out before the PRV lets go.

Ally
Ally
Reply to  Fix My Compressor Moderator
December 11, 2015 10:02 am

Hi,
Thanks for your help, I have replaced the PRV and the compressor is working as it should.
It’s a shame I had to fork out for an expensive pressure switch (£23.78) when all I needed was a cheap PRV (£2.99).
So my advice to anyone with the same problem try replacing the PRV first before replacing the pressure switch.

regards, Ally

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Ally
December 11, 2015 11:22 am

You are welcome. We understand about the added expense yet, if you kept the old one, you now have a spare pressure switch.

Kerry McDonald
Kerry McDonald
October 5, 2015 10:16 am

I have a Lincon 80 Gal air compressor that is feeding a commercial machine that requires 35psi of constant pressure. This demand is making the compressor to start every 3 minutes and I notice that there is still a lot more pressure in the tank that is available.

How can I maximize the use of most of the pressure in the tank, if possible?

If this is not possible, what other alternative can I do the reduce the cycling of the compressor?

Someone suggested to attach a second 80 gal. tank. Will this work?

Thank you.

Kerry

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Kerry McDonald
October 5, 2015 4:03 pm

If, for example, your air compressor has a cut in of 90 PSI, and a cutout of 125 PSI, every time the air pressure in the tank drops below the 90 PSI pressure level, the compressor will start Kerry.
If you are pulling air from the tank to your machine at 35 PSI, and the compressor starts to rebuild pressure every 3 minutes, then you are consuming a significant quantity of air from an 80 gallon tank in that 3 minutes.
You could adjust the cut in pressure of the compressor pressure switch downwards, so that the compressor would start less frequently, as long as, when the air compressor is running, your machine air consumption is less than the output of the compressor so that the air pressure in the tank will rise and shut off the compressor, as opposed to running and running and never stopping.
You need to be aware of the duty cycle of your compressor too, to ensure that it does not run longer than is safe for it, from a temperature buildup standpoint. If the motor overheats, the compressor will shut down.
You don’t indicate the HP of your compressor, nor do you indicate what the flow demand of your machine is at that 35 PSI.
Adding a tank would give you an additional reservoir of pre-compressed air to be used before the tank pressure dropped to cut in, and that would help too, as long as you keep the duty cycle limitation in mind.

Kerry McDonald
Kerry McDonald
Reply to  Fix My Compressor Moderator
October 5, 2015 7:19 pm

Thank you for that information. I am now better able to troubleshoot my problem.

Keep up the good work.

Tom Morgan
Tom Morgan
June 19, 2015 1:55 pm

We haven a eleven gal compressor that just recently continues to run constantly-I replaced the pressure switch but that did not fix the problem the compressor still runs. It never reaches the cut off pressure nor the PRV setting. The wiring is correct and there are no apparent air leaks. Can you help me please?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Tom Morgan
June 19, 2015 3:46 pm

We’re not sure what more we can add to the page on this site, https://fix-my-compressor.com/compressor-will-not-build-pressure/ , Tom. Maybe you can have a look at this page, and then add a comment telling us what you found? Also, if you do comment, please add the make and model number of your compressor. That always helps. By the way, if you kept the old pressure switch, then you now have a spare. The pressure switch was not part of the problem found when an air compressor runs and runs, and doesn’t build pressure past a certain point.

groose
groose
June 17, 2015 6:53 am

i have two stage compressor ingersol rand , while reaching cut out pressure the compressor doesn’t get stop wheres it takes 5 second after the electrical conductor get chattered with large rough sound it stops . tell me the solution plz

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  groose
June 17, 2015 10:36 am

We wish we knew the model number of your Ingersoll Rand compressor, so we cold have a look at the type of pressure switch yours has. If we are right, we suspect the chatter you hear is the points inside the switch, and that points to … perhaps, a switch diaphragm or spring issue. AT $30 – $50 or so for an off the shelf compressor pressure switch, that might be a relatively low price to pay to see if that solves the problem. If not, then you have a spare switch.

B rian
B rian
January 4, 2015 7:50 am

I have a small compressor that won’t shut off. The pressure reaches the PRV is max. I replaced the pressure switch. It was a small 2 wire cylinder. I don’t think you can wire them wrong. Does this mean the new switch is faulty?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  B rian
January 5, 2015 11:29 am

In our opinion, if the pressure in the compressor tank bypassed the normal cut out pressure setting, and the compressor runs and builds pressure to the point where the PRV valve lets go, and assuming that there are no other wiring issues (fused lead or point or some such ) then we would expect that it’s the pressure switch that is at fault.

Fix My Compressor Moderator
Fix My Compressor Moderator
October 7, 2014 10:04 am

Hello Andrew. In order for the compressor to keep running past the normal cut out pressure setting on the pressure switch, the pressure switch cannot be tripping to off at the cut out pressure.

Assuming that the new Devilbiss compressor pressure switch has not failed, the only other thing that comes to mind is that it is wired incorrectly.

Since the wiring is fairly straightforward, and I expect you mirrored what was the wiring on the original switch when you replaced it, then it must be that the pressure switch itself is not working.

You say it’s got the same pressure settings as the old. I wonder if that’s so?