Help me diagnose dead air compressor!

[MackMan]

At my shop today on a few odds and ends and the compressor was running fine. Later it won't start. I checked the breaker and it was tripped but resetting it didn't get the compressor running. Also switching the compressor on did not trip the breaker again.

First and obvious is to check for power at the outlet but what after that do I check?

It's a Kobalt 80 gal, 4.5 hp 3 cylinder 220v single phase.

Any ideas?

 

[kaffine]

Looks like there is a red reset button on the motor is it tripped?

Check for incoming power and check to see if power is making to the motor. Not sure if that compressor just uses a pressure switch or if the pressure switch controls a motor starter.

 

[Jetfixr320]

The motor may have a thermal switch? Try to reset it.

Can you turn the pump and motor by hand? Make sure the compressor is switched off before trying to turn it, in case it kicks on. That would hurt.

 

[MackMan]

I pressed the button to no avail. If it were tripped would it be sticking out?

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[Jswain]

Unplug it and open the cover where the wires run into the electric motor, one of them may have vibrated loose. If the plug end is removable check that as well

 

[MackMan]

Thanks for all the suggestions, will check these out.

 

[EOC_Jason]

Yep, I would throw the breaker at your panel, and make sure all wire connections are tight, not just on the compressor but however you have it wired to the wall.

Also make sure you can spin the pump by hand and that something hasn't locked up.

 

[MackMan]

It's wired to the wall with a standard 220V plug (looks like a 110 but one of the prongs is 90 degrees to the other)

 

[safetyman665]

Is there an on/off/auto selector switch? If there is you want to check that it's not in the off position. I know it's one of the obvious things to check, but even those can get the best of us on a bad day.

Also, when it stopped running did it make any unusual sounds? Or did it just not want to kick on when the pressure dropped below the set point?

 

[naru]

Sounds like your garden variety "start switch" problem.
Centrifugal switch should supply power until motor spins up and then kick out.
Real common for the contacts to go bad.They are like a set of points.
Symptoms will be identical to yours.
Open it up and have a look.
Sometimes simply cleaning the contacts will suffice,sometimes you need a new switch assembly.

I got my compressor for free because of a bad start switch.
It is almost always the reason an AC motor will not start.
I have repaired several.
Good luck.

 

[pattenp]

Check power at line side of pressure switch. If you have power on the line side, reduce tank pressure to where the pressure switch should turn on and check for power on the load/motor side of the pressure switch. If no power then pressure switch is bad, if power then motor start capacitor is bad. With your comment that the breaker was tripped leads me to think it has a bad start capacitor.

 

[naru]

Yeah,if everything else checks out,replace the capacitor.

 

[MackMan]

Now i'm thinking of a stupid question, but where would the pressure switch usually kick in? This compressor is new to me, and I don't really know where the cycle starts/finishes. Is it possible that it's not starting just cause the pressure isn't drained enough? I forget now what pressure it was at when I tried it.

Then again the breaker was tripped which would indicate something else wrong, but still that would be a short/sweet answer to this problem.

 

[TAMPAGT07]

Yeah,if everything else checks out,replace the capacitor.

Yupp...I'm betting capacitor...

 

[Dustball]

Now i'm thinking of a stupid question, but where would the pressure switch usually kick in? This compressor is new to me, and I don't really know where the cycle starts/finishes. Is it possible that it's not starting just cause the pressure isn't drained enough? I forget now what pressure it was at when I tried it.

Then again the breaker was tripped which would indicate something else wrong, but still that would be a short/sweet answer to this problem.

Bleed off some pressure and see if it turns on again. Yours probably turns on at 125 psi and off at 155 psi.

How many amps is your circuit breaker and is anything else plugged into the same circuit?

 

[MackMan]

Good news, I got it too start, however it needed to go below 100 psi. Stopped below 150. Tank says it should go to 155. Probable the pressure gage is inaccurate or is there an adjustment for that? Seems like it should come on at a higher pressure.

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[EOC_Jason]

If you have another gauge I would hook that up to verify the existing gauge is accurate. I had one on my tank forever and one day I decided to hook a 2nd one up temporarily, just using an air fitting to the end of the hose. Found out the old gauge was off by 10 psi.

You can usually adjust the cut in / off pressure by adjusting two screws. If you do some googling there is a nice PDF with a bunch of different styles explaining how they work. Sometimes too on the inside of the pressure gauge cap there is information. Make small 1/2 turn adjustments and only do one at a time to figure out what is going on.

 

[MackMan]

Well, it occurs to me that I effectively have 2 inline gages. There is a gage on the regulator, and with the regulator wide open the gages match, so unless they are both off by the same amount, probably rules that out.

I found a PDF of the compressor manual but they don't say what the pressures should be and they say to not tamper with it.

It's not that critical to have a higher pressure, the only thing I have that requires high pressure is a tire changer that's supposed to have 145 or so PSI, but probably not something that's going to be used frequently.

So I guess I'll go try to find that PDF.

 

[compressornew]

Check regulator and starting indications of machine.Is power consumption is ok ? ? ? while turn on the machine.Attached machine wires on stabilizer and check turn on to off machine indications.On other way i suggest for replace air filter of machine.Sometimes compressor machine doesn't consume proper air filters through machine and interrupted the machine.

 

[EOC_Jason]

Usually 150 PSI is the max for single-stage compressors... Check what PSI your pop-off valves are too, if you go too high they might start venting unintentionally.

My compressor doesn't kick on until like 85-90 psi... But then again I don't even use anything that requires high pressure, usually I'm just filling tires or blowing stuff off.

 

[MackMan]

Thanks, it may be well within spec, but I don't see a spec anywhere so it's hard to say. Since it says 155 max psi I was thinking it would maintain above 100, but it may be fine. Only thing I have that requires high pressure is the tire changer, so I'll just need to make sure I use it when the tank is freshly pressurized..

 

[Dustball]

This is where I found the pressure switch numbers-

http://www.manualslib.com/manual/512284/Kobalt-137603.html#manual

I took a guess at your compressor model number based on what I could see in the picture.

 

[MackMan]

That does appear to be the right compressor. Mine seems to be more like 100 to 145 though.. Wish they had instructions on how to adjust it, but guess it's not a huge deal.

 

[Russ.W.]

Checked the oil? No oil will lead to seized pistons. I know that first hand. once turned on, it'll try for a moment, then trip the breaker.

 

[pstnbly]

Unloader is not working properly.

 

[MackMan]

Checked the oil? No oil will lead to seized pistons. I know that first hand. once turned on, it'll try for a moment, then trip the breaker.

Oil level is good, but I do need to change it.