Air compressor has difficulty starting
#1
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Air compressor has difficulty starting
My air compressor is having trouble starting up. It seems to stutter. It rarely starts up and runs normally. I've replaced the motor start capacitor and that has not helped.
Here is a video of what it's doing:
https://www.youtube.com/watch?v=ml4BYHCjwgw Here's what I know since I started troubleshooting:
The check valve is NOT the problem
The pressure switch is not the problem
It's much worse now that it's cold outside and will not EVER fully start.
Any ideas?
Here is a video of what it's doing:
https://www.youtube.com/watch?v=ml4BYHCjwgw Here's what I know since I started troubleshooting:
The check valve is NOT the problem
The pressure switch is not the problem
It's much worse now that it's cold outside and will not EVER fully start.
Any ideas?
#2
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Since it seems to start when there is no air in the tank, I'd suspect the unloader valve, which is usually attached to the pressure switch. It's designed to relieve back pressure on the pump while it is starting.
It would help if you'd provide model number of the compressor.
It would help if you'd provide model number of the compressor.
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It is an oil bath compressor and the oil is new and filled to the proper level.
It's a craftsman 921.153101
I don't think it's the unloader valve, when it does eventually fill up and I turn the switch off while its running, it does release the pressure. The video is a little older too. As it sits right now, the compressor will not start properly, even with 0psi in the tank.
It's a craftsman 921.153101
I don't think it's the unloader valve, when it does eventually fill up and I turn the switch off while its running, it does release the pressure. The video is a little older too. As it sits right now, the compressor will not start properly, even with 0psi in the tank.
#5
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I guess that leaves two things (well, three). Run capacitor, starting switch, motor winding. I know you replaced the start capacitor, but bad run cap could also cause. Assuming it has a mechanical starting switch I'd open the motor and make sure it's not clogged with dust. Unlikely you have an open winding, given it's gradually gotten worse, but it's possible.
Oh....I'm assuming the shaft spins relatively freely and you don't have a bearing frozen....
Oh....I'm assuming the shaft spins relatively freely and you don't have a bearing frozen....
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It's much worse now that it's cold outside and will not EVER fully start.
On the other hand, it IS a cheap, direct drive machine. It is not built with longevity in mind. It states in the instruction manual it has a maximum duty cycle of 50% and a maximum use time of 30 minutes per hour. Usage beyond this can (and most likely will) damage the machine. It could be that it is just plain worn out.
#9
Nothing wrong with my compressor... but I know that if I expect it to run the next day, I can't leave it sit outside overnight during the winter.
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I've been "playing" with air compressors since my age was in single digits.
During the 26+ years I worked for one company I spent as much time with air compressors as I did with boilers and I NEVER saw a compressor that used 30 weight oil in the crankcase. Our rotary screw compressors (250 horsepower to 800 horsepower) all used a 10 weight, or maybe it was 5 weight, automatic transmission oil, the centrifugal compressors (400 to 1,750 horsepower) used a 10 weight hydraulic oil and the reciprocating machines (175 to 1,200 horsepower) used a 10 weight mineral oil in the crankcase along with a 90 weight cylinder oil in the cylinders. With the rotary screw compressors we eventually went with a proprietary synthetic oil that was no more than a 5 weight equivalency. The centrifugal machines all had external lubrication systems that ran 24/7 keeping a minimum temperature of 100+ degrees even when the compressor was shut down.
Even in the small reciprocating compressors used in home shops and also instrument air installations never used anything heavier than 20 weight oil in the crankcase and IF they were subjected to lower temperatures they used a 10 weight oil.
During the 26+ years I worked for one company I spent as much time with air compressors as I did with boilers and I NEVER saw a compressor that used 30 weight oil in the crankcase. Our rotary screw compressors (250 horsepower to 800 horsepower) all used a 10 weight, or maybe it was 5 weight, automatic transmission oil, the centrifugal compressors (400 to 1,750 horsepower) used a 10 weight hydraulic oil and the reciprocating machines (175 to 1,200 horsepower) used a 10 weight mineral oil in the crankcase along with a 90 weight cylinder oil in the cylinders. With the rotary screw compressors we eventually went with a proprietary synthetic oil that was no more than a 5 weight equivalency. The centrifugal machines all had external lubrication systems that ran 24/7 keeping a minimum temperature of 100+ degrees even when the compressor was shut down.
Even in the small reciprocating compressors used in home shops and also instrument air installations never used anything heavier than 20 weight oil in the crankcase and IF they were subjected to lower temperatures they used a 10 weight oil.
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I would take the head off and look at what is happening with the reed valves. They often get stuck or damaged. If the exhaust valve is bent or stuck in a closed position, you may be trying to pump into a dead end.
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As far as the oil is concerned, it's some Campbell Hausfeld air compressor oil from Home Depot. I'm not exactly sure on the weight without looking at the bottle.
I did bring it inside over the weekend to try it warmed up and there was no change. I know the unloader valve is working because once it does eventually build pressure, it hisses for a second when I turn it off.
I don't think I'm going to pull the head apart because it does build pressure even while its running weird.
I did bring it inside over the weekend to try it warmed up and there was no change. I know the unloader valve is working because once it does eventually build pressure, it hisses for a second when I turn it off.
I don't think I'm going to pull the head apart because it does build pressure even while its running weird.
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I don't think I'm going to pull the head apart because it does build pressure even while its running weird.
As I stated earlier, it is a cheap, direct-driven compressor and the motor under the best of circumstances is barely adequate. I'd change the oil to a straight mineral oil of no more than ten weight and then just run the thing until it totally craps out.
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Well, I have to get it to run consistently first before I can run it until it totally craps out.
Where would I be able to find some of the oil you mention? Everything I'm finding online is either 30wt or like $40/gallon. I really only need a few ounces for this thing.
Where would I be able to find some of the oil you mention? Everything I'm finding online is either 30wt or like $40/gallon. I really only need a few ounces for this thing.
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Try an auto parts store. Look for the absolute cheapest 10 weight oil they have. You could also use cheap, no-name automatic transmission fluid but the cheap oil would be better. What you want is something light weight and slippery. Steam turbine oil is ideal but I doubt that you could find a source for just a cup or two.
If all you need is a few ounces then you might find some ten weight "Three-In-One" oil in the hardware section of Wally World.
If all you need is a few ounces then you might find some ten weight "Three-In-One" oil in the hardware section of Wally World.
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OK. New run capacitor will be here today. It was cheap, and from amazon, so easy returns if it doesn't fix it.
Now oil. I'm having a hell of a time trying to find anything other than 30 wt compressor oil that's affordable. I know 3-in-one oil was mentioned. This says SAE 20 on it, but would this work? http://www.amazon.com/gp/product/B00...=sr_1_3&sr=8-3
Now oil. I'm having a hell of a time trying to find anything other than 30 wt compressor oil that's affordable. I know 3-in-one oil was mentioned. This says SAE 20 on it, but would this work? http://www.amazon.com/gp/product/B00...=sr_1_3&sr=8-3
#19
OMG, get a quart of air compressor oil. Its $5.
http://www.truevalue.com/assets/prod...rge/687566.jpg
http://www.truevalue.com/assets/prod...rge/687566.jpg
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So I installed the new motor run capacitor. All the specs match the 'old' one, but no go. I even tried warming up the crankcase for a few minutes with a 500W halogen work light. It struggled for 20-30 seconds, then tripped the breaker. I'm done.
Anyone want this thing for parts or to fix? $20 in the Milwaukee, WI area.
Anyone want this thing for parts or to fix? $20 in the Milwaukee, WI area.
#24
You say the check valve is ok because the pressure switch bleeds air when the compressor stops but did you remove the discharge line to see if it will start when open to the air?
It is possible that the check valve or discharge line is partially plugged causing a restriction on start-up.
It is possible that the check valve or discharge line is partially plugged causing a restriction on start-up.
#26
I don't think it's the unloader valve, when it does eventually fill up and I turn the switch off while its running, it does release the pressure.
https://www.air-compressor-guide.com...essor-unloader
I have just replaced the whole pressure switch when mine has had startup problems and it fixed the problem.
The pressure switch is not the problem