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Air Compressor Won’t Start? Ways to Fix Air Compressor Won’t Turn On Problems

Published Categorized as Air Compressor Won't Start 52 Comments on Air Compressor Won’t Start? Ways to Fix Air Compressor Won’t Turn On Problems

An air compressor not turning on is a very common issue. Knowing how aggravating it is, this article will provide the reasons your air compressor tries to start but won’t, and a few of the tips in hope that they will help you get your air compressor back on track and working effectively.

Table of Contents

Why Won’t My Air Compressor Turn On?

  • Power issue
  • Fuse or breaker blows when starting
  • Air leaks
  • Faulty pressure switch
  • Faulty compressor motor
  • Faulty unloader valve
  • Insufficient oil

Air Compressor Won’t Start – Power Issue?

Is the air compressor’s electrical power plug intact? However, the basic principle for electric compression systems is to connect the machine to a wall socket.

Silly question I know, but is the compressor electrical power plug in the wall socket? Avoid power bars and power strips because they don’t support the direct connection of machines to electricity sources. This should be your first check!

You should be careful if you intend to use an extension cord because they come in different gauge ratings. To avoid choking the power that goes to your compressor, use extension cords that have between 10 to 25-gauge wires, if you must use one. Visit our what size extension cord for an air compressor guide for more information!

Air Compressor Won't Start? Ways to Fix Air Compressor Won't Turn On Problems

Plugin all okay? Then your next check is… Can you get to the electrical service/power panel in your garage or house? Have a look inside it and see if any of the breakers are tripped, or fuses are blown. If so, reset the breaker or change the fuse.

Or, plug a trouble lamp into the same socket that the air compressor will be plugged into, to make sure that there is actually power getting to the socket.

Air Compressor Won’t Turn On – Fuse or Breaker Blows Again When Starting

Any form of mechanical equipment that uses electricity often works with circuit breakers. Circuit breakers will trip off when a power surge blows their fuses. These circuit breakers offer protection for power panels and equipment. They could trip off to protect your air compressor when there’s a very high voltage. If the fuses are bad, you will need fuse replacements before starting your air compressor.

If the compressor is creating an electrical fault, then the breaker will pop or the fuse will blow once the compressor tries to start again. If this is the case, and your compressor still will not start then you should look along the wiring path for your compressor and make sure it has an in-line fuse, that it hasn’t blown, or if there is a thermal reset button, give it a push.

Having done these quick checks, you will now have identified for sure that the air compressor is the source of the electrical problem.

If the breaker or fuse lets go when the air compressor tries to start but won’t, you have an electrical problem at the compressor. That might be the compressor pressure switch shorting out, a start capacitor has failed, or the motor is failing or overloaded… there are a host of reasons, covered on the troubleshooting pages on this site.

Air Compressor Not Turning On – Is There Pressure in the Tank?

The next check should be looking at the gauge on the compressor tank. Is it showing pressure? Is that pressure reading higher than the high-pressure cut-out of that compressor? Sluggish build-ups of receiver pressure can affect the operations of air compressors.

The accumulation of dirt in air tanks can impede an air compressor’s pressure rebuild process. Usually, manufacturers recommend air compressor owners clean or change contaminated air filters.

Air leaks from loose joints also lead to lagging receiver pressures. However, air filter replacements and tightening of joints should resolve these problems. You will notice a slow receiver pressure buildup when the Husky air compressor won’t turn on. It might be from its insufficient compressor speed.

Air Compressor Not Starting – Is It the Pressure Switch?

Check the pressure switch of the compressor if it does not start. Unplug the compressor from the electrical outlet before opening the drain valve releasing the air from the tank down to zero and then closing the drain. You can attach a blowgun to the drain valve to help empty water vapor and air from your compressor tank properly.

I would advise wearing safety goggles for this process. Pull the cover from and get down close to look into the pressure switch and have someone else plug the compressor back in or turn it on. Do you hear anything happen? Do you see any movement in the pressure switch?

Air Compressor Won't Start? Ways to Fix Air Compressor Won't Turn On Problems

You might hear a click as the pressure switch trips due to low pressure and the points in the pressure switch should move, to allow them to connect, and send power to the electric motor. Even an ultra-quiet air compressor’s pressure switch will produce this sound.

If you hear a click from the pressure switch when the compressor is powered up and you see the points move, then the pressure switch seems to be working, and it is now sending power to the motor.

Can you check that? If you have a multimeter, you can check to be sure that power is actually flowing across the pressure switch to the motor circuit. And, if you have that multimeter, you don’t have to kneel and listen, just dump the air from the tank, power up the compressor, and check if power is getting to and flowing through the switch.

If the motor does not start at this point, and it is getting power, what is the motor trying to do?

Air Compressor Motor Won’t Start – Humming Compressor Motor?

Are you hearing a humming sound, or is any noise coming from the compressor motor? If not, double-check for a thermal overload button or a reset button on or around the motor. With the compressor plugged in, push that button. What happens?

If the compressor motor starts, this suggests that it went out on thermal overload, and you may have an overload or motor overheating problem.

To check, when the tank pressure gets up to the cut-out level, and the compressor stops, bleed the pressure down again. If the compressor restarts, well, just carry on. the motor has cooled sufficiently to allow it to restart.

If the compressor motor balks at starting again, it may be the start capacitor or the motor itself that is causing the problem. Or…

Air Compressor Will Not Start – Faulty Unloader Valve?

If your air compressor tries to start but won’t, it may be worth monitoring the unloader valve when the compressor cuts out (if the compressor starts once it cools) to make sure the unloader valve is working.

If the unloader valve does not operate as it should that may be why your compressor will not start the next time the pressure switch sends power to the compressor motor.

When the unloading valve is faulty, it either stays in an open or closed position. A closed unloader valve will provide your compressor with startup problems. Also, these faulty unloader valve problems might trigger a blow-down of compressed air. However, there will likely be a continuous leak of compressed air with a stuck-open unloader valve.

If the air compressor won’t build air pressure due to a faulty unloader valve, install a replacement valve from another brand. However, it’s crucial to ensure that your replacement valve aligns with the connection of your compressor’s pressure switch.

Air Compressor Is Not Starting – Insufficient Oil?

Oil-lubricated air compressors need a constant supply of oil to be able to run efficiently. When the pump’s oil level is below the manufacturer’s specification, your air compressor might well be in danger. You should check the oil level, and inspect the pump area for any potential leaks.

When your air compressor’s oil viscosity is off, you’ll need to drain and replace the oil immediately. Refill the oil tank with lubricants that have the right viscosity. If you put the wrong compressor oil in your machine, you could get away with the mistake in the short term but, the oil’s additives will likely cause damage to the compressor pump’s components at a later date. It will give a knocking-like sound when the air compressor tries to start but then it won’t run.

Normally, mechanical systems that require oil won’t turn on when their oil levels are low. It’s a safe way of shutting down the system and protecting other components. To fix this simple problem, move your air compressor to an even platform and additional vibration pads.

FAQs (Frequently Asked Questions)

What causes an air compressor not to start?

If an air compressor is unable to start, it’s likely due to a problem related to an air leak or a damaged part. However, you could also be having power supply issues or the compressor contains insufficient oil.

Is there a reset button on an air compressor?

Yes, air compressors have thermal reset buttons (often called thermal overloads or cut-outs) wired onto the motor or on the side of the compressor. The purpose of this button is to automatically turn the air compressor off if it overheats.

Why did my compressor suddenly stop working?

I would first check whether the compressor has overheated, causing the thermal overload the trip the compressor off and not allowing it to start until it has cooled. Otherwise, it could be a problem with numerous components such as the motor and circuit breaker.

Reader Questions & Responses

Air compressor just stopped working?



I just picked up an Iron Man 5hp 2-stage compressor that the guy said just stopped working. It’s 220v and it’s on its own breaker. When I plug it in I can hear the contacts on the switch engage but nothing happens. I’m sure if I left it plugged in it would blow the breaker. Everything spins freely. The capacitors look a little rough, can I check to see if the motor is junk before buying new capacitors? Thanks


If the pressure switch trips on when power is applied to the compressor and power are flowing through the switch to the motor circuit, and then nothing happens, I suspect it is either a start capacitor or motor problem. See the page on this site about testing your capacitor first to see if that has failed. If not then I would suspect the motor has pooched and needs to be tested.

Campbell Hausfeld VT629002AJ Compressor Will Only Start From Empty


Hello Bill,

I have a Campbell Hausfeld VT629002AJ 20-gallon oil-type air compressor that has had an issue for a long while now and I am trying to sort it out. The compressor will start from empty and fill all the way with no problem but has a hard time starting when it tries to kick on as the tank is being drained.

When it does fill to cut out I can hear a loud hiss from the unloader valve (so I assume it is working) also when partially full I can hand turn the pulley and hear air escaping from the valve… I did replace the check valve, but that has had no effect. At this point, I am wondering if it could be the electric motor. Thanks in advance for any insight you could give. Jordan B.

Ways to Fix Air Compressor Won't Turn On Problems
Campbell Hausfeld 20 Gallon Air Compressor (VT6290)


Hey Jordan. Yup, it sure sounds like your unloader valve is working OK and that lets out the first and most common reason why an air compressor will not start when there is air in the tank.

What’s next? There’s a page link on the troubleshooting page about compressors that won’t restart when the air is being used, and I believe your answer and much more info will be there.

Meantime, I suggest you visit the page on this site about how to check the motor capacitor(s). I suspect that a failing or failed capacitor is the main issue.

If the compressor was working properly before, and you haven’t relocated it to a new power supply, that is.

There may be other issues but these are the main two. Check out the cap, and give us an update as to what you found if you would. Thanks.


Can you tell if your machine was made before or after 2001? It may not matter if your motor capacitor is bad, but maybe if the cap is good. Please let us know.

Compressor With 1 HP and 12 gallon Tank Won’t Start


I have an old model Air compressor 12 Gallon 1 Horsepower. My problem is when you plug it in, it looks like the AC outlet might be shorted and gonna burn my fuse.

If I knock the motor body with the plastic hammer and then it gonna starts the motor and when the pressure will reach the maximum setup and then the motor will create noise and then the power with kick my fuse burn.

Please let me know what issue is this. In my opinion, I am thinking that the capacitor is the main problem but I don’t know yet where I am going to buy this.

Please I need your help.



Hi there George… so, when you plug in the air compressor it “looks” like the plug is going too short?

Hard to be specific with an answer not knowing the make and model of the compressor.

Your compressor symptoms suggest to me that you have a short in the compressor and if this were mine I’d start by checking to see if the pressure switch was operating properly.

That you whack on the motor to get it going also suggests that your compressor motor may have a centrifugal start mechanism that is failing.

Depending on how much time you want to spend on this compressor George, you can pick up a low-cost 1 HP compressor for under $100 dollars these days, and you could either replace the entire power train of your existing compressor with the new one, or, use the existing compressor only as an extra tank, and fill the tanks on both air compressors from the new one.

If you are a tinkerer though, then there will be lots of value to you in trying to figure out what’s going on with the older air compressor.

Please add a comment here with your findings so we all be updated.

136424 Husky Compressor Won’t Start


Hello, I’ve been working for the past month on reconstructing a 15 x 20 outbuilding that has been slowly decomposing into mud since it was built in 1930. I had to jack up one side of the building because of the rotten wood and the whole structure sagging.

Husky air compressor model 136424
Husky air compressor model 136424

Anyway, my Husky Compressor, Model No. 136424, 155 PSI, 19 Gallon has been getting a workout. Similar to the Husky 8-gallon air compressor won’t start. I’ve been running mainly nail guns for the past month. I plugged it in as usual and it worked fine for half the day when I noticed that my framing nail gun wasn’t working quite right.

I went to the tank gauge and it read 40 PSI.

I checked the electrical outlet and all the other electrical tools were working.

I bled down the pressure to try and activate the sensor switch and nothing happened.

I plugged it into the extension cord by itself and nothing happened. I thumped on it a couple of times and nothing happened. I’m baffled.

How does a perfectly good compressor just quit working?

I bought it from Home Depot a couple of years ago. I don’t know if I have the original receipt. I don’t know what’s covered under warranty or if it is even eligible. I really haven’t used it much until this past month.


Ron, use a multimeter to check and see if power is actually flowing through the pressure switch to the motor circuit.

If the tank pressure is zero, then the pressure switch should have tripped to “passing” and power should be flowing to the motor. If it is not, then your pressure switch is suspect number one.

However, I suspect from what you have written that you have been underpowering your air compressor for quite some time, by using an extension cord. It is known that your extension cord, if not big enough (allow enough power flow) powers the motor, and the motor runs hotter than normal, and wears out sooner.

So, if you have power to the motor circuit, next check the capacitor(s) (see that page for how to do that) and if they are good, then you possibly need a motor check-up.

Compressor Won’t Start Unless Tank is Empty?


I have an 80gal 220v Delta compressor and if there is any pressure in the tank it will try to start and struggle and then trip the breaker after about 6 seconds.

I replaced the pressure relief valve that unloads the pressure from the pump and I even put on a start capacitor and run capacitor (I hope I have all the terms right since it has been over a year since I did all this). The only way it will fill is if it is 10psi or less. Any pressure above 10psi will trip the breaker. I really need to get this working correctly since I now need to start using it more than I have been.

Any ideas about what could be the problem?

Much appreciated.


Boy, I wish you had uploaded a photo of your Delta compressor. I was unable to find one to help me understand the issues.

However, one reason the compressor motor won’t start – and blows fuses or breakers – is because the motor draws too many amps on startup, exceeding the capacity of the circuit breaker, and it pops.

A common reason for the excessive motor load on startup is that the compressor hasn’t unloaded properly when it reached cut-out pressure and stopped.

To be sure that this isn’t your compressor problem, bleed the tank to zero pressure, start the compressor, and let it fill to cut out pressure.

Observe and listen to your unloader valve to be sure it activates when the compressor stops. If it doesn’t that’s your problem.

Since you appear to have corrected any potential problems with the motor, please also check and see what else is on the supply circuit to the compressor. If another device is starting or running and drawing power from the compressor circuit when the compressor tries to start, that too could be causing a problem.

Please comment on this thread to let me know if the unloader valve is not, for sure, the problem.

Repair for Compressor Model TC-20T


My oil-less airbrush compressor overheated after an hour of use and it will not start back up.

I’m assuming I burnt out the motor because the air compressor thermal overload switch did not shut off the compressor before it overheated, if it did it would have turned back on later.

Do you have any ideas on how to repair it?

What should I look for once I take it apart?

Any ideas on how to extend the time I have to use the compressor continuously between rest periods?

Thanks for your help, Robert

TC-20T air brush air compressor
TC-20T air brush air compressor


Robert, your air compressor comes with a two-year warranty, so, if the failure is within this time frame, get a warranty repair or replacement.

When you were using it, did you have it plugged in with an extension cord? If so, you may have been underpowering the motor, this makes them run too hot and may have contributed to your compressor problem.

The specifications also say “Thermally Protected: Automatically turns itself off if the unit becomes overheated” based on what you write, this did not happen, and you may have damaged the motor.

The thermal switch is just that, a switch in the power line from the plug to the motor. They aren’t complex and can be replaced, though unless you are an electric motor repair person it may be challenging.

Your compressor appears to be manufactured in China by:

Ruian Royal Air Tools Company,
Bldg.2, Shuangfeng Cun, Fengshan Road, Luofeng, Tangxia Town, Ruian,
Zhejiang, China 325204
Tel: 0086-577-65320601
Fax: 0086-577-65320602
Email: [email protected] 

Website: www.airbrush-airbrushcompressor.com

Airbrush www.royalairbrush.com

Contact Person: Mr. Jay Foo (Sales Manager)

In your shoes, I’d be getting in touch with them for assistance.

Compressor Won’t Start – Heard a Spark…That Was It!


I tried to plug it in when the on switch was turned. I heard a spark and that was it. No nothing. It’s a 26 gal. Kobalt.


Thanks for writing in. A model number for the Kobalt would sure help, as would a picture or two.

It’s pretty hard to diagnose the problem with the info provided.

The spark you “heard”, was it from the pressure switch, the motor, what exactly?

Did your breaker pop or fuse blow for the circuit when the spark occurred?

It would certainly seem from the info provided that it’s an electrical problem, yet you need to provide quite a bit more information to help try to figure out what’s what.


Your problem could also be a weak wiring issue.

You may have a bad connection, a failing outlet, too long an extension cord, really any number of things could cause the same symptoms.

The easiest way to tell if it’s the wiring is to plug in an incandescent bulb as close to the compressor as you can, on the same circuit and extension cord if possible.

If it dims way out when it’s trying to start with pressure, or if it dims a lot before it shuts down at full pressure, it’s an electrical supply problem.

If you hear the ‘whoosh’ of air when it builds pressure and shuts down normally, the unloader is working properly.


Now that’s an excellent tip! Use a trouble lamp in the same circuit to get a visual of how much power is being drawn as the compressor starts.

Kobalt Compressor Model 215914 Will Not Start


The Air compressor display works but will do nothing.

Kobalt model 215914 air compressor
Kobalt model 215914 air compressor


Hi Tom… listen, could you pop over to the troubleshooting page on this site and see the info page about why air compressors don’t start?

There are some things noted there that you can check and when you’ve done them, please add a comment here to tell us what you’ve done and seen as a result, and we’ll press on with helping you figure out why your Kobalt 215914 won’t start.

Just don’t want to retype the same information here that is already there for you to use, OK?


Kobalt 60G A/C Hums and Won’t Start


Kobalt 60 gallon air compressor
Kobalt 60 gallon air compressor

I have a Kobalt 60G upright a/c, I was using it one day recently and while it was running, building pressure, the motor stopped and started to hum. Before I got to it to shut it off it blew the breaker. I changed the breaker and tried to start it, but when I turned the switch on, it turned about 1 revolution and then started to hum and then flipped the breaker. It has done this once before, but back then it wouldn’t even turn. Turned out to be the capacitor(s). Is this the problem? Since it tries to start, could it be that only one capacitor is bad?


Hello Jason. If the motor was running and the air pressure did not reach cut-out pressure, and the motor suddenly stopped and would not re-start, my bet is that your air compressor motor won’t start and is at fault, not the capacitor.

My thought is that if the capacitor had failed, your motor wouldn’t have enough oomph to even start turning, and after the built-in delay in your circuit, the breaker would pop.

Your motor may need a rebuild.

The only other thing I would do before I took the motor and capacitor in for testing, and only if I was comfortable doing so, is to bypass the pressure switch, flip the breaker on, and see what happens. There may be an outside chance that your problem is caused by a faulty pressure switch.

Cheers and good luck. Maybe let us know how it works out?

Ingersoll Rand T30 Air Compressor Three Phase Air Compressor Will Not Start?


Ingersoll rand T30 Air compressor will not start with a diesel generator. It has been wired up correctly to a 20 amp rated three-phase male socket. My electric air compressor won’t start.

The air compressor was dormant for many years and was recently acquired after a disposal/ auction sale.

Both the V twin motor and Toshiba electric motors are not seized as they can be turned by hand. The compressor has an auxiliary power board where it can be started and turned off. I wired the four wires correctly as what was previously utilized in the auxiliary switch box. The fifth wire was black and was not used. The wires used are red, white, blue, and green/yellow.


Stan, this is well beyond my capabilities. I am happy to post your question with the expectation that those more learned than I may respond.


Of course, you could always liaise with IR directly? company.ingersollrand.com

Husky VT6311403 AJ Has 220 Volts on Pressure Switch?


I have a VT6311403 AJ 60 gal husky electric air compressor that won’t start.

This unit is made by Campbell Hausfeld and I spoke with them today. Similar to a Craftsman 150 psi air compressor 15 gals won’t start!

I have two 110 legs hot on both sides of the wall plug reputable when you go to one hot wire and ground.

If you test both 110 at one time the meter shows 220.

At the pressure regulator switch, you have 110 on the black and 110 on the white same on the motor terminals 110 each.

The tech from Campbell Hausfeld said you should be able to touch both 110 wires on the pressure switch and it should read 220 volts.

Well, when I touch both black & white terminals on the pressure switch at one time I get nothing at all but when I touch them one at a time and ground them I get 110 volts.

What am I doing wrong? He said the problem was in the breaker box I think he is wrong because I have changed out the breaker with another double pole 20 amp from another one that I know works for sure

I have even gone so far as to tie the wall plug to another location in the breaker box that I know for sure that is a working breaker and still nothing the 3.2 hp air compressor motor won’t start.

I just don’t know what to do anymore need some help, please!



Russ I am not going to comment on the electrical side of things as I am not an electrician.

I was unable to find specifications on your air compressor online.

So, I am going to assume that your compressor is wired for 220 volts, and if the breaker is wired correctly and the pressure switch has the leads in the right locations, then, if the tank pressure is below cut in, you have power to your compressor motor circuit.

If you have power flowing through the pressure switch to the motor circuit, and there is no reaction from the compressor when you power up, my first thought is that something is halting the power from getting to the motor and that something is often the start capacitor.

Your question is live now. I hope someone with an electrical background can comment on your wiring questions.

There is a page on this site about how to check capacitors, as well as another page about all of the things that you need to check when the compressor won’t start, both under troubleshooting.


Using a double pole 20 amp breaker one black on one pole and one white on the other pole one green to ground bar. Yes the motor is wired for 220 it has a tag that says 220 only


Lost 220? OK, to recap, you have 220 at the outlet, but only 110 at the pressure switch.

The only way that could happen is if one side of the 220 is open between the plug/outlet and the switch, and the switch is “ON”.

With the switch “OFF” you’ll likely see the 110 on one pole and nothing on the other.

If that is the case, you may have a bad power cord.

Check that with an ohmmeter. Unplug the compressor, and measure resistance (ohms) from one pin on the cord to the switch. One side of the switch should read near zero ohms. If not, repeat with the other plug pin just to see that at least one side is zero ohms. Then fix the open (high or infinity ohms).

If that doesn’t pan out, please send pix of the cord plug end and the switch end.

Have fun.

IR 175 With Deutz 3 cylinder Has No-Start Issue


I have an Ingersoll Rand 175 air compressor with a Deutz 3 cyl diesel F3L912 that I can’t get it to start.

(History) I bought the unit used about 18 months ago that was totally rebuilt. I had been setting but after cleaning the tank out and bleeding I got it running and has been a good unit.
Recently In 2 Weeks the engine on the first start in the Morning would turn over but won’t fire until the 4 or 5th attempt (lots of black Smoke out of the Exhaust). After the warm-up, it would fire ok and run fine.

Now I can not get it to start at all. I thought it could be a fuel pump issue so I replaced it, with a new fuel filter, oil + filter. Bleed and Bleed 30Xs.

Won’t fire off. Lots of black smoke and carbon out of the exhaust.

IR 175 compressor 3 cylinder Deutz motor
IR 175 compressor 3 cylinder Deutz motor

I took off the air filters clean them, removed the muffler, blew it out tried starting with it off to no avail. Could not find anything blocking airflow intake or exhaust.

It’s almost like there is something electrical that keeps it from starting.

I do notice the speed flow regulator cylinder Has some sort of weep hole when trying to start there is air being blown off.

I can get the engine to spin over longer with one of the injectors cracked than with it closed.

Could it be an injector issue that keeps it from firing?

Timing with the valves?

Injector pump?

Maybe some sort of relay that I’m not aware of that does not allow a start cycle.

I know of the belt tensioner sensor that has a shutdown. Is this pin supposed to be depressed or unobstructed? I tried running a jumper wire to it, no difference.

I know someone who has had one of the compressors might give me some aid.

Nobody local knows about them.


Does it use glow plugs?

If so, then the circuitry for those can be screwed up, consistent with the electrical theory.


It doesn’t have glow plugs.

(Up to date) After checking thru all circuits I wound up opening up a relief valve that was close to the compressor pump. When trying to start, it would kinda run on for 5 seconds. After playing with it I got it to run by continuing to hold in the fuel by-pass button for an extended length of time.

First, it struggled to run (thinking injector #2 was bad) then it finally caught on.

After it ran for a while and warm up it would fire right up. I’m waiting on an injector pull tool to service or replace them.


Do you know if the injectors were replaced on the rebuild?

If so, then maybe you should recheck the fuel system for debris.

Thanks for the update, and keep us posted on the injector findings, please.


I’m still waiting on my injector pull tool. I’m going to pull them all in the next week or two. Check them, service them or replace them.

My Jun Air Compressor Not Working


Inadvertently ran the thing out of oil. Filled the oil so that I see it in the little bubble window but now the compressor tries to start – the green light comes on for a second or two – then it shuts off.

This cycle repeats every two minutes or so.


Without having the compressor here to take a look at, all I can surmise from your post is that your compressor has reacted to the lack of oil and has become damaged.

If the pump became really hot, for example, the piston may have seized in the pump, and since the motor is connected to the shaft that drives the pump if the pump cannot move then the air compressor motor won’t start.

That you see the green light indicates to me that the power is getting from the pressure switch to the motor.

Jun Air 6-25 air compressor
Jun Air 6-25 air compressor

Depending on your skill set, see if you can access the pump crank and, after disconnecting the motor, see if the pump piston will move.


Just wanted to thank you for the ideas. I pulled the cover off of my pump and located the crankshaft. I inserted a screwdriver into the slot on top and tried turning it. There was a little bit of binding at first but before long the lubricant got in and made it smooth again. I put the top back on and it’s been running like a champ since.

Thanks again! your site is truly helpful.


You are most welcome. Glad to have been of help.

Why Is My Air Compressor Not Turning On


It turns over very slowly and then trips the breaker. I have to shut it off and then wait for the click and retry several times before it eventually speeds up and starts, Any ideas seem like there is a load on it but I have tried two brand new units with the same results.

Thanks, Bob

Questioner #2

I too have a Harbor Freight compressor that wouldn’t start when cold without repeatedly popping its thermal reset switch. I moved the compressor to another branch circuit, and it fired right up. Both circuits are 15A, but there are several other appliances on the first circuit, and I think there just wasn’t enough juice left for the compressor. (Both outlets are outdoors, so the temperature is not a factor.)


I discovered after only two days that to cold start my 21-gallon vertical compressor the tank needs to be empty. Starts right up every time now. Ironically it should be empty and free of condensation before it is stored. Easy fix.


I suspect that the reduction in back-pressure load, created by draining the tank, is the most important factor in helping your central pneumatic air compressor 21-gallon won’t start.

Yet, draining the tank after every use is recommended, so it’s a win-win, regardless of why this helps the central pneumatic air compressor won’t start. Good stuff!


I found that when I drain the tank the compressor starts right up without hesitation and functions properly. Thanks for the affirmation.

Clarke Air Compressor Will Not Start



I have a Clarke air industrial 150l piston compressor that’s about a year and a half old, it worked perfectly until today.

We noticed earlier that it was starting sluggishly, now it starts sluggishly sometimes and works fine, other times it turns once and the overheat switch cuts in and stops it, then it continues to do this for a few mins till it eventually starts fine again.

Clarke air industrial 150l air compressor
Clarke air industrial 150l air compressor

It can’t be the cold as winter where I live has barely set it yet, and it ran last winter fine. It’s wired in the same way it has always been and has always worked fine.

I just can’t understand how it works sometimes and not others. I would just like to add that it still starts sluggishly even when it does work and the psssshhhht sound is heard when it fills up.

It also doesn’t work more times than it does.

Please help as soon as you can as I’m really stuck and I run a small car repair center (uniquecustoms.co.uk) and we have a van to paint by end of the week and this is my only compressor as the other 200l is dead too.

Thanks, Matthew


Matthew, no change in power supply, nothing else pulling power from the same circuit sometimes when the compressor is trying to start? Make sure the power source is clean.

Turn off the compressor, dump all the air from the tank, close the tank drain, and start the compressor. Any change? If it starts fine with no air, I suspect a sticking unloader valve, or perhaps the pressure switch is not tripping fully or properly, and the unloader isn’t getting opened every time, or full power isn’t flowing to the motor when it is supposed to.

Next guess… start capacitor, though I would expect that to be a constant problem rather than intermittent if it was failing.

Give us some feedback as a comment, please.


No change to the power supply or anything added or taken away but have noticed a small valve on the heat sink on the pipe that goes out from the pistons into the tank that seems to be sticking and making more noise than it used to.

I assume that this valve opens when the compressor starts to allow airflow into the tank and closes when it stops to keep it in the tank. I would assume then that if it sticks closed on startup then the compressor is overloaded and it cuts out.

I also assume that the sluggish startups that work are sluggish as the valve is slow to open. I want to check the next time it cuts out if the valve has opened and if it hasn’t then I would say that’s the prob. However, it hasn’t failed yet today so until it does I cant say.

If this does turn out a problem can I fix it? Is it OK to unscrew it and clean and oil it just don’t want to break it.

Thanks for all your help.


Before doing any work on the compressor, unplug it, and drain all the pressure from the tank. Then, fill your boots. Enjoy!

Husky Pro Air Compressor Motor Won’t Start?

Some time ago Tom wrote in with a question about why his Husky Pro air compressor motor won’t start. Little response was offered by the visitors to this site then, so I thought we’d ad a bit of information here if you have a similar air compressor and the motor will not start.

This is a Husky Pro compressor with an 80-gallon upright tank and a dual-stage pump.

The Husky compressor motor that wouldn’t start is a WEG brand (www.weg.net) and was a 4 HP unit. This motor came equipped with both a “start” and a “run” capacitor which you can see in the photo below as the two “bumps” on the top of the motor. Those “bumps” are the capacitor covers.

Air Compressor Won't Start? Ways to Fix Air Compressor Won't Turn On Problems

Tom also said that he bought this as a used air compressor. When he examined it the owner started it up during the demo. It started slowly but started.

The fact that the Husky Pro started slowly when Tom was looking at it before buying would suggest there were some issues. That may have suggested a pump seizing issue, a blockage of the air path between the cylinders or down to the tank, or a motor problem.

An early step may have been to remove the belt and try to turn the pump sheave by hand to try a feel any binding or lockup. It should turn reasonably easy, and that may give a good indication as to whether the pump may be the problem.

If turning the pump sheave gives the impression of binding or locking up, that may point to mechanical binding or valve issues in the pump heads or in the valves themselves. If the results suggest the pump may be the issue, it’s likely time to remove the initial pump head cover and have a look at the valves within. It may be necessary to replace the gaskets as they may get damaged in the removal and reassembly process.

If all looks good remove the headcover from the second cylinder and perform the same examination, with careful checking of the intake valve that controls the intake air from the first stage, and then examine the high-pressure valve to be sure they are not the issue.

If all seems OK, then check the tank check valve. Make sure it allows free flow of air from the pump head to the tank.

If that’s all OK, it’s time to look at the motor.

With the belt still off start the compressor motor. Did the motor start? Was there any sluggishness or slow starting?

A check of both capacitors would be next. Here’s a page about how to test compressor motor capacitors.

Last, if the caps check out, then that likely points to the motor itself being the problem, and a motor check will likely require taking the motor to a rebuild testing house and asking them to check it out thoroughly, particularly with a heavy load test.

Good luck, and let us know what you find if you have to go through this.

Champion Compressor Runs Only When You Hold The Reset Button


Hi, I have a Champion compressor advantage series. All of a sudden the compressor will not start. It was found that they did not drain for a while. So we opened the valve and a lot of water came out.

Champion Air Compressor
Champion Air Compressor

After that, we power the compressor and it will not start. It will start only when you hold the RESET button. If you release the RESET button, it will stop, Please advice

Thank you,
Sudhakar Tammireddi


You are powering the compressor with a 240-volt feed I expect, though I don’t know if yours is the 5 HP or the greater HP compressor.

The reset button is often a thermal cut-out, shutting power to the motor if it starts to overheat.

If the motor is cool, and you have to press down on the switch for the compressor to run, it may be that the thermal overload switch itself has failed.

If the motor is overly hot and you continue to over-ride the thermal cut out, then you will likely be damaging your compressor motor.

Does the same symptom occur if you try to start the air compressor with the tank empty of air?


Thank you for the update. This compressor has been running for the past 2 years with no issues. It just started behaving recently.

We drained the tank completely. The only way it runs is when the RESET button is pressed.

The moment we release the RESET BUTTON the compressor stops. All the electrical connections are as per requirement.

We used to drain from the safety valve earlier instead of draining from the bottom of the tank and this built lot of water in the tank. Now we have drained completely but still this problem. Looking forward to your advice.


I surmise that the reset button itself is at fault if the air compressor won’t even try to start when cold.

To test the theory remove it from the circuit briefly by jumping a wire around it. If the compressor starts then you know it’s the reset switch, and a replacement should solve the problem. I recommend that you do NOT run the compressor for any length of time without the reset, except for the brief period of testing.

If the Champion still doesn’t start, please comment.

Why Won’t My Compressor Turn On


My Mac 5200 won’t budge any noises, strain, clicks, or vibrations. Just quite dead. There’s the power to the pressure switch when I flip the unit on (as measured by the voltmeter), so whatever’s going on sits deeper inside it.

Makita 5200 Air Compressor
Makita 5200 air compressor

Hints: I used it last week, and all was fine; then I drove it 200 mi. It clicked and chugged briefly before it died,

Rats. Any & all ideas are most welcome.



With the tank empty of air, use your meter to see if power is crossing the pressure switch to the motor circuit.

If so, then power is getting to the motor, and the absence of any sound would indicate that the motor isn’t trying to start.

That being the case, see the page on this site about testing your start capacitor – under troubleshooting – as that is the likely culprit.



There is a thermal overload switch mounted near the fan end of the motor. I don’t know if it’s supposed to reset or if it is manual, but it’s worth a look.

If that’s the immediate problem, then I’d check the capacitors while you have them apart.

Questioner #2

This comment is not about another compressor…. my mac5200 did exactly the same thing.

Worked fine yesterday running one framing nailer. then this morning turned it on weak tried to start then nothing.

Had my buddy test the switch he said the switch is fine. This compressor’s second season of what I consider light use…I work alone doing home improvement.

Couple roofs couple additions carports every year… I expected many years of trouble-free use… pretty disappointed.


My apologies. I guess I misread your original post.

Tell me, has anyone tested the start or the run capacitors on your Makita 5200 compressor? The symptoms suggest that it/they may be the issue, and that may also suggest that you use the air compressor for long periods of time at one time?

Sullair 185 Diesel Will Turn Over But Won’t Start


Sullair 185 will turn over but won’t start even by spraying a little starting fluid in the breather.

Sullair 185 air compressor
Sullair 185 air compressor

Is there a disconnect at the compressor so it won’t pump while trying to start?

Starting fluid should at least make it fire, shouldn’t it?


Starting fluid should at least make it fire, shouldn’t it?

Yes, although that’s a dangerous thing to do…

Having said that sounds like no compression.

The air end should be unloaded during the start phase,

If it is cranking, and you feel the air going in the intake, then it’s either rings or valves or timing gear. Might also be not enough air into the cylinder – check the intake filter, or maybe remove it temporarily to test.

You didn’t let it run dry (fuel), did you?

Campbell Hausfeld Compressor Will Not Start

What can you do when your Campbell Hausfeld compressor will not start? Here are questions sent in by visitors, and responses about this Campbell Hausfeld compressor problem.


I have a 60-gallon, 5hp compressor. I just installed a new pressure switch that cuts in at 140 and out at 175. After running for a while, I got nervous and flipped the pressure switch to the off position. Now when I toggle the switch to auto, it doesn’t make contact unless I take the cover off and manually push to make the contact. Did I ruin my new pressure switch and how long does it typically take to build up to 175psi?

Campbell Hausfeld 5 HP air compressor
Campbell Hausfeld 5 HP air compressor


You have replaced a pressure switch, right? The new one cuts in at 140 PSI and out at 175 PSI, and this makes you nervous? How come?

Is it because you are trying to run your compressor at a higher pressure level than the original switch? If you are, my advice is… don’t!

What is the air pressure in the tank when you “get nervous” and trip off the pressure switch manually? If the tank pressure is higher than the 140 PSI cut-in pressure, then your pressure switch will not trip to on automatically.

Try this. Shut the power off, drain the tank to zero PSI, leave the pressure switch alone, and power on the compressor. What happens?


Thanks for your quick response. I didn’t have a gauge at the tank, so I didn’t know the pressure there. That is why I was nervous. I just wanted to make sure it was working properly before use since I fixed it myself. I opened my in-line gauge at the moisture trap to 175 and it shows the compressor cutting in at 125 and out at 160. Please forgive my ignorance. I believe my compressor is working as it should now. Thanks!

Questioner #2

A 5hp 60gallon Campbell Hausfeld won’t start – this air compressor is really old thinking maybe around 20 yrs, anyways runs great but goes through a pressure switch at least once a year, use it for automotive body repairs and paint and automotive mechanical repairs but no constant just side work.

I keep replacing switches with Campbell Hausfeld brand, replaced the check valve, but have come to find that one of my two capacitors is swollen, I am in the process of ordering one but was wondering if you think this is the reason why it keeps going through pressure switches or do I need to give up on this air compressor, I would like to quit replacing switches like this, they get expensive after a while. thanks for your help.


After 20 years, I’d say this air compressor doesn’t owe you a lot. A $30 repair once a year is sure a lot less than buying a new, and perhaps not nearly the same quality as your original, air compressor.

From your post Burton, I can’t determine what it is about your compressor pressure switch that is failing?

If it is a point burnout, could be a supply voltage problem, or could be a capacitor/motor pulling too much current on startup.

Folks tend to add other electrical devices over time, and if some of them are pulling from the same power feed as you have to your air compressor, it is possible that it’s not getting enough power to run properly, and that is sometimes manifested in burn switch contacts.

If you have any questions about why your air compressor is not starting, please leave a comment below, with a photo if applicable, so that someone can help you!

By Aidan Weeks

A passionate Mechanical Engineer with endless enthusiasm for fluid power - building off the back of over 18 years of high quality contribution and discussion stimulated by Bill Wade here at About Air Compressors. With both practical and theoretical experience in pneumatics and hydraulics, I'm putting my knowledge to work - and working my grey-matter through my research, assistance and publishing work here at About Air Compressors. Feel free to reach out any time! P.S. A HUGE shout out to Doug who really offers such great value to all visitors to About Air Compressors - once again, feeling like I'm standing on the shoulders of GIANTS by getting to work alongside such a great community

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