Air compressor will not start

It isn’t any fun when we go to use an air tool and an air compressor will not start to allow the air tool to be used. Very darned aggravating, indeed.

There are many types of air compressors in use around North America, and though many of them look different than other air compressors, and they certainly vary in size and other area, there are similarities that will allow you to check and see why “an air compressor will not start , by yourself and hopefully not taking it to a shop which is both expensive and time consuming.

To try an help you diagnose why your air compressor will not start, here are the steps I would use on my own air compressor.

Is there power to your air compressor?

Wall socket and plugI know, I know, it’s a dumb question, but needs to be asked.

If you are using a power bar or power strip… don’t! Plug your air compressor directly into a wall socket. The power strip may have failed.

If you are using and extension cord… don’t! You are putting a choke on the power to your compressor unless the extension cord is 25′ or less, and at least 10 gauge.

Move the air compressor to get it close to the wall socket, make sure there is power at the wall socket, and plug your compressor in there.

Air compressor will not start …  read on!

Is the compressor switch on?

If your air compressor is one of those that comes with an ON/OFF switch, either separate from or part of the pressure switch, do please make sure that it is switched to on.

Of course, if you have been using the compressor and it won’t start, the power switch will likely be on already. But just in case, please check it anyway.

What is the air pressure in your compressor tank?

When my air compressor will not start I always check the tank gauge to see what the pressure reading is in the tank.

The reason for that is if the pressure switch is set with a cut in pressure (the setting at which the air compressor will start) that is below the air pressure currently in the the compressor tank, then your compressor pressure switch has not tripped to on, no power is flowing to the air compressor motor, so the motor cannot start.

Even if the air pressure in the tank is below the air compressor cut in pressure setting, part of the diagnosis as to why it won’t start, is to empty all of the air out of the compressor tank.

Try emptying the compressor tank

Unplug or shut off the compressor.

Air compressor PRV and air compressor tank drain

Drain the air tank by attaching an air tool or blow gun to the hose and blowing off all the air, you can drain the compressor tank by opening the tank drank valve and allow all air (and any trapped water) to blow out the tank drain which you should do regularly anyway, or you can empty the compressor tank and test your air compressor pressure relief valve at the same time, by pulling on the PRV ring (wearing gloves is a good idea). This will allow all the air to blow out of the tank as well as making sure that the PRV internal workings actually do work. After all the tank air is gone, push the PRV valve back in and your PR Valve is reset.

Why empty the compressor tank?

By draining the tank you are emulating the function of the unloader valve just in case the one on your air compressor is not working properly. A complete description of what the unloader valve is and does is on the unloader valve page.

Emptying all of the air from the air tank allows any air trapped over the compressor piston – or compressor pistons – to escape out through the tank as well. If there was trapped air, the additional load on the air compressor motor may have prevented the compressor from starting.

OK. Plug your compressor back in or turn it on… any luck with it starting? No? OK then, let’s carry on.

My air compressor will not start – still!

We know we have power from the wall socket to the compressor, we now know that a malfunctioning unloader valve isn’t the problem, we are going to assume that if your air compressor has an ON/OFF switch that it is turned to on, so now what?

Is power getting to the compressor motor?

Knowing that power is getting to the compressor does not mean that power is getting to the motor. Besides the ON/OFF switch that might be in the circuit between the wall plug and the compressor motor is the pressure switch. If the compressor pressure switch has not tripped to allow power to flow through it to the motor, the compressor cannot start.

Unfortunately, if you don’t have a poke probe or a multi-meter you will have a difficult time doing the next check.

Comments or questions are welcome. Please use the comment box below. More information about compressor starting problems is available on the next page. Follow the link… more reasons why an air compressor will not start.



  1. Mac Gyver says:

    Hi, I was wondering if you might have any information on a Rockworth Classicair 2 gallon air compressor? I received this from a friend because it was dead. I took off the cover and noticed that a 3A fuse was blown, so I replaced it and tried to power it up and it blew the fuse right away. The motor is a 120VDC Model PM301DF if that might help any.
    There are only 2 components on the board with the fuse and they are a bridge rectifier and a yellow rectangle small component with might be a capacitor of some kind.

    Manually turned the motor and it seems to move freely without any binding.

    No burnt marks on the circuit board.

    I figured I would ask the experts here to see if anyone has any ideas of why it is blowing fuses.
    Also, would you know if the 3A fuse (which is marked on the board) should be a slow blow or a fast blow fuse? I have a DMM if You need to me check voltages or readings, just let me know what you want checked. Any help would be greatly appreciated.

    Thanks in advance. Have a good day

    • If the fuse blows almost instantly, that suggests to me that there is a short somewhere, possibly in the motor windings. I am not familiar with this circuit board myself, so will not comment on the components. I hope somewhere out there who is familiar with compressor will add info.

  2. Hi mate i melted my start capicitor after starting issuse after long run periods on my compressor.
    I have since replaced the start capacitor with an equivalent 50uf capicitor but my compressor still woll not start.
    It has power it has no air in it it spins freely its turned on and i have plles the presure release valve, all i can hear is a humming sound that was the same with the old melted start capicitor installed.
    Any ideas what i might be missing?

    • A humming compressor is one that has an electrical issue, and the most common cause of that is a capacitor. Does your compressor have two capacitors, and if so, did you check them both. If not, is it a start / run capacitor that you used, as a start cap isn’t a run cap, and vice versa.

  3. My compressor would not start and i started researching why. And looked here and there…and maybe i am just lucky because it sure wasnt my diagnoising abilities. But my compressor has a reset button. Shabam it started right up. So check and see if you have a reset button before getting to far in. It might be that simple.

  4. Cory L says:

    I have a power built hot rod 5 gallon air compressor. When I tried to start it this morning, it came on for a few seconds, then died and came on for about another second, then died. When I turn the switch it clicks but doesn’t start

    • willyr says:

      If there was a time period between the compressor trying to start, that was probably to let the motor cool, as it sounds as if it’s going off on thermal cut out. If this is a new problem I would look at the capacitors on the motor. See the page on this site about how to test them. If it’s an ongoing problem, make sure you’ve got no extension cord, are plugging the compressor plug right into the wall socket, and there aren’t other big-power-draw items on the same circuit as your compressor.

  5. have a june air OF1202-40m , start when on button is push, but does not stays on if button is release, replace pressure switch no changes, any ideas?

    • willyr says:

      If you are saying that pushing the ON button allows power to flow to the pressure switch and then the motor, and releasing the button stops the flow of power, then it’s likely the button itself that has failed, not the pressure switch. Is it a rocker switch, a detented ballpoint type, where you push ON and it locks, and push ON again for it to pop out? Regardless, if you use a power meter to check the switch side of the ON button, and when you release it, the power stops, then it’s the switch.

  6. Steve man says:

    Hello Nil,

    I have Husky model FP209102, its hardly used. After I used it for the first time,fill it up and left it ready if I need it. I expect that if the pressure to go below certain level it should start again . It didn’t. So I thought that the pressure switch was faulty, I replace it with new one, it worked again filled the tank but again when the level went down it will not start,
    So I found out that if I give the crank lever or turn the attached gear it wil start . I tested by manually letting the air in the tank to go down below the required level and the compressor start, But then if I leave the compressor for a day it will not start and the same problem.
    It need another push to start. I know this type of compressor is oilless as specified, even though I tried to spray wd40 on the crank lever connection but it didn’t make any difference.
    Any idea what else I can do.
    Thank you in advance

    • Steve, have a look at the page that refers to testing the compressor motor capacitor. That would be the next step if this were my compressor.

      • Steve man says:

        Thank you for the advice, unfortunately, switch on the compressor push the big gear little to kick start it. it ran for a while, then start giving funny sound, the motor overheat and the circuit breaker went off ,
        I guess the motor has died. I m not sure if it worth to fix any more
        I m very disappointed with the quality of Husky. Very bad workmanship.

        • Sure, but did you check the capacitor? They aren’t expensive, and if your start cap has failed, then replacing it may fix the problem, and save you the cost of a new compressor.

  7. Jack Miller says:

    Once my compressor stops it won,t restart even after the pressure drops —until it has set awhile. I can’t even turn it over by hand.

  8. I bought a brand new titan industries air compressor, it is wheel barrow type with 2 four gallon tanks. I believe previous owner started both engine and compressor with no oil in them. Is any of it salvageable? I’m thinking the pump might be?

  9. Don Gitzel says:

    Here’s my problem. I have an industrial grade compressor with a huge pump and a 7.5 hp 3 phase motor. I have purchased a 15 hp phase converter to operate on residential voltage. It will trip the 2 pole 40 amp input breaker upon start. Here is the normal sequence of operation. When the compressor reaches a set point of 150 lbs, the pressure switches off the motor contactor electrically and mechanically unloads the compressor head through a small relief valve. This valve closes after the unload. Now when the next start up is called for, the head is rapidly loaded before the motor can com up to speed. This creates too much load and the breaker trips. If the blow down line is removed from the pressure switch not allowing the head to load, the compressor starts fine. I think I need a centrifugal unload switch or a electric bleed off switch with a timer. Any thoughts

  10. Hello, I have a ridgid tri stack compressor. In new condition that I am trying to fix. When you plug in the compressor it starts to run but is hesitates and never fully starts. Not like the humming or buzzing of the motor. Also you can see the motor sparking inside the case. I do have it plugged directly into a 20amp socket. I have changed the start cap and overload switch. I have it torn down to the motor and see where the wires are plugged in. I am wondering if it is the run cap or if possible the wiring in the motor was backwards or something. The motor also has 3 other terminals with nothing connected.

    Any help would be great!!! THANKS!!!

    model # OF50150TS

    • Certainly check all caps. Then, I wonder, do you know if this motor has a centrifugal switch? If so, it sounds as though it’s seized in the run position and not flipping back to the start wiring.

  11. Can’t seem to get it started this morning have to do it with pull rope usually starts right up doesn’t even act like I am pulling

  12. Wow, I empty my comp. tank, direct plug into the wall socket, restart and it works well. Thank you for your guide.

  13. I have a quincy 7.5 compressor. We have it wired to a 30 amp breaker. the compressor does not have a start or stop switch. I kick the switch and the breaker kicks, no power, nothing engine wont move…nothing happens. Its also brand new, never started and no pressure at all. Help?

    • If it’s new, was there not a startup kit or instructions included? Regardless, if you cannot get it going, call them to come take it back. But first, find the manual and follow the steps.
      That the breaker kicks out instantly suggests that there is a short to ground somewhere. That’s what you have to look for. Be careful. 240 VAC is dangerous.

  14. Daniel Litchfield says:

    I have a 10 gallon job smart, won’t start, it has power to it. How can I bypass the switch to check it?

    • Daniel, a bit difficult to answer as you don’t indicate the model number of the Jobsmart, so I cannot find it on line to see what pressure switch you have. Please upload a photo. If it is the one I think it is, you don’t need to bypass the switch. It’s better to empty the tank, plug the compressor in, and use a multi-meter to ensure that power is getting to the switch, and then, with the switch cover off, that power is actually on the motor side of the switch when the tank is empty. Follow the power from the motor side of the switch to the capacitor on the motor to ensure power is getting that far. If so, it might be a capacitor problem.

  15. Hi

    My air compressor motor isnt turning on , i changed the capacitor and still doing the same thing
    if you plug it it , n turn it on , it hums but fan or motor doesn’t turn on .

    Please help me sort this out

    • Not knowing the make or model of your compressor makes this very hard to do, Mohamed. Tell us about the make and model, how you are powering the compressor, and how long that this problem has been occurring. We’ll try to help, though reviewing all the troubleshooting pages on this site that apply will give you more things to check.

  16. Shawn Coker says:

    Compressor had air over the piston. This site solved my problem quickly. Thanx,

  17. Christie says:

    I have a 5.0 cfm 90 psi 2 HP. The plug in works. I was using it last night and it was working fine now all its doing when I turn it on is hums…..its a 4 gallon. What’s wrong….?

  18. I have bambi 150/500 bambi air compressor for dental clinic.
    my compressor keep overloading.
    any advise how can I solve this problem?

    • Milad, please provide more details. What do you mean by the compressor keeps overloading? Thank you.

  19. Lynard Brock says:

    My 2 hp 8 gallon air compressor just stopped coming on. I left it plugged in all night, it has a small air leak in the hose connect that makes it kick on when it gets low enough. It’s from harbor freight tools. When I went out the next day it was out of air, still plugged in, but wouldn’t come on. I have a like a breaker switch on top with a red push or pull button, and it does nothing when I push or pull for off and on. The outlet works, why did my compressor stop working? Thanks

    • We need to know if you have done the recommended checks, Lynard. Is there power to the socket, is there power getting to the pressure switch, is there power on the motor side of the pressure switch with the tank empty. The red push or pull button may be an ON/OFF button, and if so, you need to check to be sure that the power from the cord is actually getting through the switch when it is in the ON position. Or, this may be a thermal cut out switch, meaning that it cuts power to the compressor motor when the motor is getting too hot. That could happen when a compressor cycles too frequently, as if it had a big leak, or was being used in high air demand air tools. We need to know more about what you have checked to answer further. Thanks.

  20. Philip ryder says:

    My compressor starts and runs fine on initial start up but will not restart when pressure drops. It will only restart when I push the little red button on the back of motor but only when motor is not real hot. On a cooler day compressor will restart sometimes twice before having to let motor cool down enough for the red button to restart. Thx

    • The red button you refer to Philip is probably the thermal cut out. That trips the motor off if it starts to overheat.

      I think that the page already provides the answer you seek: “Why empty the compressor tank? By draining the tank you are emulating the function of the unloader valve just in case the one on your air compressor is not working properly. A complete description of what the unloader valve is and does is on the unloader valve page. Emptying all of the air from the air tank allows any air trapped over the compressor piston – or compressor pistons – to escape out through the tank as well. If there was trapped air, the additional load on the air compressor motor may have prevented the compressor from starting. I suspect your unloader valve is not working. Please check it and advise if that is not the problem.

      OK. Plug your compressor back in or turn it on… any luck with it starting? No? OK then, let’s carry on.

  21. My husband doesn’t dare to ask for help. It must be an ego thing…. He has a Maxair 12 gallon. It doesn’t start. I read and shared your instructions and nothing seems to work. I know that he removed the switch, the tank is completely empty and he said that he has power in the solenoid switch. He’s ready to hammer it to pieces … Do you have any suggestions. Thank you in advance Lise

    • Maxair 12 gallon air compressor

      Oh my, taking a hammer to the compressor won’t help getting it running… normally.

      We see that some things have been checked, but don’t know if all the items on the pages about why air compressors don’t start have been checked. They are found here: // . Perhaps you might add a comment about what the findings were when you checked each item?

  22. My compressor is not starting. I disconnected the belt to check the motor is working, and it is fine. Once I reconnect it, the onboard circuit breaker trips. Tank is empty. Any suggestions?

    • the circuit breaker is likely tripping out due to the motor drawing more power than is available to start it. Some easy things to check are… are you using an extension cord? If so, don’t. If the compressor is plugged directly into a wall socket, are there many other items on that same circuit trying to pull power when the compressor is trying to start? If so, that might be your compressor problem. Have a look at the pages listed under the problems and solutions column. Maybe start with this one: //

    • Among others in the Problems and Solutions column is this page. // If you haven’t, look at it and other pages referring to compressors that are hard to start or blow breakers. Your circuit breaker is tripping as the motor is pulling too much power under load and that exceeds the capacity of the circuit. It may be that not enough power is getting to the motor too, then it would overheat, and trip out. So, make sure the power supply is clean, no extension cord, no other appliances pulling power at the same time as the compressor, and if that doesn’t do it, we would suspect the start capacitor. See that page and how to check it on this site.

    • My air compressor was trying to start, turned over a couple of times then would trigger the overload breaker on the motor. I live in Australia with 240V mains. I tried removing the start capacitor (150uF 250v) (which I thought was the culprit) and same symptom. The run capacitor (35uF 450V) was enough to start the compressor when there was no air in the tank, but under load – no dice. I bought a new start capacitor, installed it and now she starts without the slightest hesitation. Victory!!

  23. I have a snap on made by Big red 20 gallon 5 hp single phase compressor, sometimes it would trip the breaker when trying to start and other times it would start right up. Now i don’t even get a hum from the motor! I wired it after removing the mounting bolts too a homemade plug..I still got no hum or noise although it was getting 110 volts..Both the start and run capacitors where attached at the time i bench tested it..The centrifugal switch and rotor seem too be fine and no burn marks on the stator..Any ideas? Thanks

  24. I have a “Campbell Hausfeld” model#. WL600602AJ Stats are= 3.5 horse 11gallon 120V/ 15.0A/ 60HZ/ 1PH SCFM 8.1 @ 40 psi. 6.1 @ 90 psi. 125psi max. It is an older model but has been a great work horse. Only problem I started having with it was it comes on automatically when plugged in. The ON/OFF switch on the compressor its self stopped working. So when ever I want it to to turn off, I have to unplug it. It does stop when tank is full, but the switch to turn off does nothing. I have checked the wires and nothing has come loose. What could be the problem? How could it always be turned on on when plugged in?

    • ON/OFF switches are elctro-mechanical devices, and they fail. It sounds like your switch has failed closed, or passing, meaning that power is flowing through the switch to the pressure switch even if the switch is showing as OFF. You can replace the switch, they are not complex, and if you Google for them you will find many sources. On the other hand, the pressure switch does an admirable job shutting the compressor off when the tank pressure reaches cut out. If your air system has no leaks, even with the compressor plugged in, once the tank is full the compressor should not start again on its own, until you use air. Or, if your system has a small air leak, your air compressor will start again on its own once the tank pressure reaches cut in. Unplug it if that is the case, or replaced the ON/OFF switch, those are your choices we believe.

      • Thanks. Yes, it doesn’t have any leaks. It shuts off when tank is full and doesn’t start again till I use air. But I will try replacing the on/off switch like you have said. I know this problem seems weak compared to what I have read about other people’s issues with compressors, but it still annoys me having to unplug and plug all the time just to stop it. Thanks “willyr” for your time and information. 👍

  25. Thank you for your advise and help. I had purchased a new starting capacitor which did not make a difference. I was about to purchase a pressure switch when I came up on your website. I simply opened the existing pressure switch box and lifted the switch plate up with a screwdriver, plugged it back in, and it started working immediately. So, thank you, once again.

  26. Greetings,

    The patient is a brand new Ingersoll Rand 2545 E10-VP, one of their “fully packaged” models. New installation. Compressor motor was rewired for 460 V and the “starter” box was also swapped for a 460V unit (I-R part). We have #8 wire running to the unit, from the disconnect. This is all fed by a rotary phase converter and a step-up transformer 240-460. All of those components seem to be operating normally, other equipment on the same supply work fine. We are testing the compressor with no other machinery on, see no voltage drop at the phase converter that would indicate a supply problem. Have a commercial electrician on the job, so all wiring has by now been triple-checked.

    Compressor’s “set” pressure seems to be 170 PSI, and from a standing start with an empty tank it will quickly startup and pump up. At about 145 PSI it attempts to fire up again to recharge and cannot. It will sometimes get a couple of spins, then groans, then the overload trips. Overload is set to 14.5V. Temporarily setting it to 15.5 has no effect.

    Much testing and head scratching has taken place, during which we discovered that if we bleed the tank pressure to as high as 90 PSI it can and will restart and recharge, but anything over 90 tank pressure causes the non-start and eventual overload.

    Reading this excellent site (and others) pointed me in the direction of the unloader switch, which I believe I have located integral with the pressure switch at the top-center of the tank (horizontal) – at the end of a successful cycle a valve is actuating and there is a 5 or so second hiss of air escaping from beneath the pressure switch. I can’t feel or detect any leaking after this cycle completes.

    It sounds like that is operating properly, but the symptoms of my issue seem consistent with an unloader switch problem. Can you shed any light on the issue,. point me in the right direction? I-R service has been contacted and I am waiting for a return call, but I certainly would value any intel I can gather too.

    MANY THANKS for this excellent site.

    • You are welcome. Thanks for visiting, and I hope we or others can help you with your IR compressor issue. Yes, it sounds as though the unloader is working properly. That being the case, to our thinking, the problem may lie with a weak or failing start capacitor. See the page on this site about how to check yours, and please let us know if that was the cause.

      • Thank you very much Willy.

        Although the unloader feature WAS venting post-recharge, it was not venting the entire piping circuit between the cylinder and the tank check valve. An I-R technician visited yesterday and when we manually vented the piping (about a 2-3 second tug on the relief valve evacuated all the pressure) via the pressure relief valve at the left rear behind the smaller cylinder, the unit started and recharged normally at it’s set pressure.

        Not understanding or seeing what’s at the end of the compressor crank where part of this system is, I can’t theorize what the specific problem is, but they assure me it will be resolved. I expect a call from them today.

        MANY THANKS for maintaining this excellent site – info on this site is what put me onto the unloader as a possible culprit and that certainly helped to resolve it faster.

  27. Hi, my 5.4 iron horse compressor won’t run. Plug receptacle is good, on/off switch is in the on position, no air in tank, power cord is good, never run out of oil.

    • Kevin, a couple of things to check, if you will. You say you have power at the receptacle. Good first check! That suggests that power is flowing down the power cord to the ON/Off switch. But, is the power getting across the ON/Off switch? You need to use a multimeter to check the motor side of the switch to be sure that the ON/Off hasn’t failed. If power is getting across the ON/Off switch, check to be sure that it’s getting across the pressure switch, as, with the tank empty of air, the pressure switch should have tripped to ON, and power should be flowing across the points to the motor circuit. If power is getting to the motor circuit, the next check is the start cap. All of this is covered in the page about air compressors that don’t start, and you will need to do these checks, or have someone do them for you, to diagnose where the fault in your air compressor lies.

  28. George J. David says:

    Dear Sir,


    We are having Euromatic Air Compressor (50 LT)

    It is set to cut off at 110 PSI and to re-start at 90 PSI, but the compressor doesn’t start.

    It wont start till the tank pressure becomes zero.

    Motor gives jerks to start but not thru at this time motor is drawing 30 Amps current.
    This is 3 times more that the staring current.

    Would like to know what is the problem?

    Is it a motor or compressor piston problem?

    George J. David

    • George, we were not able to see an image of your compressor, so cannot be sure, but feel that you need to check that the unloader valve is working. If the air compressor unloader valve has failed, there is too much load for the air compressor motor to overcome, and it clicks off on thermal overload, after drawing too many amps when trying to start.

  29. my iron horse 5.1 cfm @ 90psi portable air compressor 1hp max pressure 125 psi 6.5 gal ran out oil and wont start the tank is empty and it is pluged in to the socket what els can i do

    • Are you saying that your Iron Horse air compressor ran for some time without any oil? If so, heat may have damaged the pump and the motor. If you have power to the socket, and that confirms power to the compressor, and if the tank is empty, and absolutely nothing happens when you switch it on or plug it in, did you do all the checks referred to on these pages?

  30. My cambell hausenfield aircompressor will not start. My ground metal piece came out. I checked to see if there was air in the tank. It is a 200psi rated aircompressor can you help.

    • Johnny, we’re not quite sure what you mean by “ground metal piece”. Why not upload a photo of it so we can see what we are talking about? Also, please indicate the model number of your Campbell Hausfeld compressor too, K?

  31. I have a air compressor that popped when I unplugged it and now it wont come on

    • Be good to know the make and model, Chris. What popped when you unplugged the air compressor? Do you have power in the wall socket?

  32. Carlos Mendes says:

    My compressor won’t start because it is jammed. We changed the capacitor because it blew, thinking that would fix it, but the engine itself still sounds like it is jammed. Any ideas on what to do?

    • A bit hard to give advice, Carlos, when you don’t indicate the make or model. Assuming you’ve got a pump sheave that’s driven by a belt from the motor, if you remove the belt, can you rotate the pump sheave by hand, or is it seized?

  33. Dr.Vishal Malusare says:

    Thanks for your valuable post. After emptying the compressor tank it started by draining air out. Is there any problem with unloader valve?

    • Hmmm. Not quite sure what you mean by it started by draining the air out. If what is happening is that air is bleeding out of the unloader valve while the compressor is running and while it is stopped, then you need to read the page air compresor Tank Check Valve for details about what this is and what it does. Also have a read of the page linked from the left navigation bar about unloader valves that leak.

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