Compressors Three

This wesite receives hundreds of questions about troubleshooting air compressors.

In an effort to make some sense of the many questions received and answered, I have tried to categorize troubleshooting air compressors into similar postings on each page. This is page three of questions and answers.

If you see a post below to which you would like to make a suggestion or ask a question of your own, please use this page.

Cheers & thanks.



New compressor motor smoking....?

Question: just bought a brand new 220 volt 60 gallon air compressor turn it on and runs for approx.10 seconds then motor starts to smoke.should i return the compressor

Response: Paul, do you shut it off immediately after it starts to smoke, or have you let it run a bit? Have you checked the power supply? Since I can't see the amount of smoke, I can't be sure that it's not just a by-product of a new motor start up, or if the smoke is a symptom of a serious problem.

If you have turned the air compressor on a few times, and it's run for a while (what does the manual say about the break in?) then I guess I'd be inclined to return it. Where there is smoke, there is something burning, and that's not good if it persists.


Feb 13, 2012 -



Compressor Burning Smell from....?

Question: I have a new IR SS-5 compressor with less then 15 hrs on it and I started getting a burning smell, specially in the air. It is in a 26 x 28 residential garage and wide open to air. I drained the oil and replaced but still the same, I drained the tank and the first little bit it almost seemed like oil, a black milky water and then came clear approximately about a 1/2 cup in total drained out. I left open for a day then closed up and filled with air and right away the smell came back, any ideas?

Response: Compressing air generates a lot of heat. Some of that heat comes off the motor as it's running against load, and more comes off the compressor head and line to the tank since smashing air molecules together generates a lot of friction, and that generates heat. When you say the burning smell is in the air, do you mean around the air compressor, or coming out of the air line?

I suspect your compressor comes equipped with a thermal overload switch, which should shut it off if the motor overheats beyond the norm. I assume it's under warranty? Though it may just be a new car smell type odor, as the compressor heats up, the paint may be off-gassing. If under warranty, and if the problem persists, get the vendor to diagnose it further.

It were my compressor, I'd open the tank drain valve part way to let the air bleed, and I'd let it run continuously for a while. If it is not a continuous run model, shut it off after 15 minutes and let it cool for at least that long. Keep us posted, OK?

Air compressor problem - just stopped working?

Question: Hello.. I just picked up a 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. Capacitors look a little rough, can I check to see if the motor is junk before buying new capacitors. Thanks

Response: If the pressure switch trips to on when power is applied to the compressor and power is 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.

Air Compressor Runs for a bit then starts to shake and turns off?

Question: I have a SMC Vertical Air compressor. The compressor will start to run for a bit then it starts to shake quite a bit then throws the breaker on the electric motor of the compressor it's self. Any information would be a great help

Response: G'day, Steve. So, it runs for a bit... hmmmm? How long is that? Are we talking a couple of seconds, or couple of minutes, or somewhere in between? When it's running for a bit, are you seeing a pressure increase in the tank?

What starts to shake... the whole compressor, the motor, can you identify the item that's causing the shaking? In order for more-than-usual vibration to occur, something has let go.

I don't know your exact compressor, partially because you don't indicate the model, and mostly because there are eighty seven gazillion makes and models and I'd sure like to meet the person that could remember them all.

If there are motor mounts, check these. If there are any elastomeric mounts where the whole compressor pump and motor assembly are attached to the mounting plate, check these. Compressors vibrate like stink, and it's usually a soft, elastomere that absorbs the oscillation so that your compressor doesn't dance across the room like Fred Astaire on drugs. If you don't know who he is, don't sweat it. It just shows how old I am. :-) Keep me posted, and update the info by adding a comment if you want to chat about your vibrating compressor a bit more. As to it's shutting off, I don't know at what pressure that occurs, so is it going of on normal cut out, or is the vibration, perhaps, causing the pressure switch to trip off prematurely?


Aug 01, 2011 - by: Al

Seeing that it drops out the circuit breaker on the motor! You have an excess load or a faulty motor. As you said you had the tank pipe disconnected! - Regards, Al ( elec fitter/tools specialist)


Jan 02, 2011 - by: Steve

I have further diagnosed the compressor. It seems if I take the line that feeds the air compressor tank of the pump. With the pump line attached to the tank it never starts to build pressure and only runs for about 2 minutes then shakes quite a bit. I have need around quite a few compressors and ever see one shake like this one.


So, it gets a bit warm from running two minutes or so, and then it starts to shake? This one I've not run into before either. As a guess I would think that you've got a crack of some sort that expands with heat, cause the pump piston to run out of balance. Regardless of whether or not this guess is right, I suspect it is tear down time, and you do need to get the unit to a repair depot if you are not up to tearing it down yourself.

5 h.p. powerex m - sc151361 vs motor starts to run slow?

Question: 5 h.p. powerex model sc151361vs 230 volt single phase - when it gets ready to shut down the motor starts to run slow like it is starting to bind up

Response: When the compressor is getting close to cut out, the tank pressure is almost there, then the compressor motor slows?

I reviewed the current Powerex offerings, and couldn't find your model, so I don't know even what it looks like. (

So, check the intake filter to be sure that it's not blocking air ingestion. And, in the absence of a mechanical issue with the pump, and if it is belt driven, that the belts are properly aligned, the power supply is sufficient to the motor, then it is possibly a run capacitor that cannot provide enough juice to the motor as the load grows, or the motor is wearing out and cannot handle the load as the back pressure builds. See the page on checking capacitors on this site to test yours.