Air compressor help needed

[TKFireman]

Long story to get where I am now. 80 gallon compressor hardwired breaker-wall switch-pressure switch - motor. Been on the same independent circuit for about 10 years.

Air compressor stopped working, low pressure. I pull out the volt meter. 120 on each leg going into and coming out of the wall switch and pressure switch. 240 when checked together. Pulled cover on back of motor, same thing, getting 240 into the motor

I bought a new motor. It ran for about an 30 min and quit. Would kick on intermittently for 5 sec or so, then stop. Weird. I wound up taking the original motor to a repair shop, returned the new one. Shop says there's nothing wrong with the old one. I reinstall it, change pressure switch just incase, it runs.

It ran for about 2 hours then quit again. Same checks, still has 240V going into the motor. After a little googling, I pull the capacitor caps, the running capacitor is swollen and didn't pass ohm test. Starter capacitor fine. I replaced them both. Still doesn't work. Still has 240V going to it. No buzzing, no noise, no smoke, no burnt belt, belts turn free. It does nothing and I'm out of ideas.

Oh, and both motors have reset buttons in them, they did nothing.

Any suggestions?

 

[nadogail]

Perhaps a mechanical issue with the compressor or belt drive.

 

[The Cobbler]

I would ( temporarily) by pass the pressure switch , don't walk away from it , don't let it over pressure ... wondering if the points on the pressure switch have something to do with it . if it still does it, look for loose connections .

 

[TKFireman]

Tried that, didn't help, replaced pressure switch anyway while I had it apart

 

[oldmachinenut]

Does your compressor have a motor starter?

 

[mm08822]

Monitor the voltage at the motor while running. Does it sag over time? Use a good DVM to do this. Also monitor motor amps from 0 tank pressure to full shut-off pressure. How does this compare against nameplate fla's?

Have you checked connections in the hard-wired circuit, cb, panel stabs?

Has the motor OL ever tripped during these recent events?

 

[MovingAlong]

I bought a new motor. It ran for about an 30 min and quit. Would kick on intermittently for 5 sec or so, then stop.

Does it kick off normally as if it reached full pressure or you flipped the power switch? Or does it just stop as if the compressor itself got hot and started to seize, thus stopping the motor?

Two separate symptoms, two separate troubleshooting paths: one electrical and one mechanical.

Good luck!

 

[wyliesdiesels]

Long story to get where I am now. 80 gallon compressor hardwired breaker-wall switch-pressure switch - motor. Been on the same independent circuit for about 10 years.

80gal means nothing. what is the HP rating on the motor?

Air compressor stopped working, low pressure. I pull out the volt meter. 120 on each leg going into and coming out of the wall switch and pressure switch. 240 when checked together. Pulled cover on back of motor, same thing, getting 240 into the motor

make and model of switch?

I bought a new motor. It ran for about an 30 min and quit. Would kick on intermittently for 5 sec or so, then stop. Weird. I wound up taking the original motor to a repair shop, returned the new one. Shop says there's nothing wrong with the old one. I reinstall it, change pressure switch just incase, it runs.

did you check the centrifugal switch?

It ran for about 2 hours then quit again. Same checks, still has 240V going into the motor.

where are you testing voltage on the motor? have a pic?

After a little googling, I pull the capacitor caps, the running capacitor is swollen and didn't pass ohm test. Starter capacitor fine. I replaced them both. Still doesn't work. Still has 240V going to it. No buzzing, no noise, no smoke, no burnt belt, belts turn free. It does nothing and I'm out of ideas.

Oh, and both motors have reset buttons in them, they did nothing.

Any suggestions?

If the centrifugal switch isnt working it may not start the motor.

 

[wyliesdiesels]

I would ( temporarily) by pass the pressure switch , don't walk away from it , don't let it over pressure ... wondering if the points on the pressure switch have something to do with it . if it still does it, look for loose connections .

he said he replaced the PS in the OP

 

[wyliesdiesels]

Does your compressor have a motor starter?

highly unlikely since it has integral reset

 

[BillK]

Like nadogail said ..... is the compressor pump itself locking up ? Does it have oil in it ? Run it until it stops and then cut the power and try to turn it over by hand.

 

[cgrutt]

Not related but possibly helpful. My son's dirtbike had similar issues would run fine then lockup all of a sudden to eventually just stopped running. Worn bearing on crank and connector rod was locking up piston. Thinking you need to check pump...

 

[WillyBoy]

Did anyone say this yet? Take the belt off. Don't think about what turns freely or not, just isolate the motor from the pump.
Does it start? Does it run? How long, continuously? Go from there.
Narrowing down the problem is easier in the long run than trying new parts.

 

[MacMcMacmac]

Sounds like a broken or nearly broken lead inside the motor. I fought this with two different sets of multimeter leads about 2 years ago. Very frustrating.

 

[The Cobbler]

Sounds like a broken or nearly broken lead inside the motor.

But he had the same or similar results with a new motor.

 

[TKFireman]

I appreciate all the replies. I'll add some more info. Voltage has been checked at the breaker, wall switch in and out, pressure switch in and out, and the motor. Black to ground wire red to each leg, 120V on each leg, then red to one hot, black to the hot, 240 on each place. No noticable loose connections.

I did not check voltage or amperage while running, and I can't currently because it doesn't run at all.

I took the belt off going to the compressor and turned it on. Nothing, no noise, or turning at all.

So right now I know it has 240V going into the motor. It has a new pressure switch. It has 2 new capacitors (running and starting) that tested fine. The pump has been taken out of the equation, so no load whatsoever on the motor. And it does nothing, not a sound.

 

[TKFireman]

Trying to post pictures, I attached 2 to last post, not showing up, I tried adding to the drop image and it says there is a problem

 

[TKFireman]

 

[TKFireman]

 

[TKFireman]

Oh, and during all this, the breaker has never tripped. The small scorch on the ground wire is where I accidentally touched the ground wire and the leg right above it at the same time with the DVM lead. Threw a spark, didn't trip breaker

 

[The Cobbler]

didn't trip breaker

try resetting the breaker . off then on .

 

[TKFireman]

try resetting the breaker . off then on .

Have several times during this, while replacing things

 

[The Cobbler]

sounds like the things you haven't changed are the cable, breaker & compressor unit itself. as others have said try taking off the belt . try to run a temporary line to the unit, try another breaker . remove the breaker from the panel & look for bad connections on the buss bars

 

[TKFireman]

New breaker installed, nothing obvious to me on the bus bar, all other circuits work fine. Nothing.

Wall switch removed, wires wire nutted together. Nothing.

Belt has been removed. Nothing

I don't have a 50' cable to run to the compressor which is in a small lean to outside behind the shop, on the opposite corner as the breaker box, and my welder circuit. Only way to test it is to pull the motor off again and wire up a plug for it. So here we go

 

[TKFireman]

Motor removed. I took the plug off a welder extension cord I have. Due to my lack of connectors on hand, i had to wire nut the pigtail that normally goes from the pressure switch to the motor to the end of the extension cord to make it work just for a test. Turned it on. Nothing. Tested it, found 120V at the motor on each leg. 240 tested together. No noise, movement or smoke whatsoever. This is on my welder's circuit.

I don't have much faith in the motor repair shop that this went to. After a $40 diagnostic fee, they told me it worked perfectly. 2 running hours later I found a swollen capacitor that failed testing. Coincidence? Maybe.

I tried a new motor off Amazon with the same specs. Similar symptoms. Coincidence that I got a bad new motor? Maybe.

 

[mm08822]

Pull the end bell. Inspect wiring at cent switch.

What do the windings read (ohms)?

 

[Codyboy]

Motor removed. I took the plug off a welder extension cord I have. Due to my lack of connectors on hand, i had to wire nut the pigtail that normally goes from the pressure switch to the motor to the end of the extension cord to make it work just for a test. Turned it on. Nothing. Tested it, found 120V at the motor on each leg. 240 tested together. No noise, movement or smoke whatsoever. This is on my welder's circuit.

I don't have much faith in the motor repair shop that this went to. After a $40 diagnostic fee, they told me it worked perfectly. 2 running hours later I found a swollen capacitor that failed testing. Coincidence? Maybe.

I tried a new motor off Amazon with the same specs. Similar symptoms. Coincidence that I got a bad new motor? Maybe.

So you tried another new motor on your current wiring setup? And nothing?
Also you never said if you tried to spin the motor shaft by hand to see if it spins freely.

 

[Codyboy]

Just reread the op.
You mention a wall "switch".

Even though you've checked it and get 240 , the switch could intermittently have an open while running and it gets hot.
Then cools down a bit and bam 240 again.

I have a marathon motor from a dewalt compressor I bought at TSC.
The compressor , brand new was marked down almost 1/2 price.
I enquired about it. The guy said they sold and it was brought back because it would run for a few seconds and trip the breaker.
I said OK let's plug it in and check it out. Yep, tripped breaker.
Eh whatever I'll take a chance.
Maybe its something simple.i can fix..
Bought it fiddled with it. Hmmm, idk.

So I called dewalt customer service.

Told the nice lady on the phone the issue and 3 days later there was a brand new motor she sent . Swapped it out and works fine.
I kept the old motor and one day I'll maybe dig into it to see what is wrong with it.

So a brand new compressor for half price and a phone call and 20 minutes to replace motor. Not a bad deal.

 

[TKFireman]

Cody boy, check capacitors. They are known to trip breakers if bad.

SUCCESS!!!! Maybe...... So I got the motor to run. I plugged it back in on the rigged up extension cord and like a starter motor, and to let out my frustration, gave it a few love taps with the dead blow. I hit right beside the overload reset, and it cut on.

Here's my theory. Starting with new motor I bought then returned. It was a crappy motor, again, just theory. Old motor, running capacitor was bad, so it ran fine at the shop with no load. Underload, after some time the overload switch popped due to a bad running capacitor and wouldn't reset.

So I'm thinking that maybe, just maybe, the new capacitor will keep the overload switch from tripping. If it does, the reset doesn't work properly, but only time will tell if I'll need it anyway.

It's reinstalled and built up to pressure. I'll get out and run it for a few hours, got a bunch of sanding to do and see what happens. Again, just a theory, but it makes sense and I'm hopeful. I appreciate all of y'all throwing out suggestions.

 

[The Cobbler]

fingers crossed for you .

 

[mm08822]

Pull the end bell, check the cent switch contacts and movement.

Get any info off of the overload switch while you are in there and locate a replacement source.

 

[TKFireman]

Imma have to google how to do that

 

[Milton Shaw]

I had a compressor that went out at 30 or so years use. The motor went out so I bought a motor with identical ratings as the old motor, same hp, voltage, service factor, shaft etc. That motor started giving problems and took belt of and motor ran fine for an hour, that to me indicated the compressor bearings tightening up. I replaced the whole thing with a customer return from Northern tool. 5 HP Quincy with an unknown problem (no 240 plug at store to test with) but a nice $600 discount off sale price and full warranty. Tried it and not running so called Northern and mechanic from 150 miles away was there within a week with new motor. It's been working great for two years now.

 

[BurtEggley]

good luck. Sounds like the reset switch is bad. Might consider trying to find one and replace it.