Compressor Frustration

[gregwils]

I have an old CH 5HP 20Gal compressor that I can't seem to get working properly. I don't use it frequently, but keep it maintained - oil/drain. About a year ago, the motor started to struggle as the pressure built. At about 80 PSI, it seems to slow just a bit and you can hear the belt (new and adjusted correctly) just start to slip as the motor puts up greater and greater resistance to spin. The pressure in tank is about 80 PSI and the pressure switch (90/125) is new. The motor isn't even hot when this occurs.

The best way I can describe it is it seems to be fighting back pressure in the tank. I removed, then polished and cleaned the check valve, but no luck. I guess I could just replace it, because I don't know how to verify it is working.

If the motor spun, but the pressure didn't get higher then I would look into a rebuild kit. I don't think that is my issue?

Any thoughts or suggestions would be appreciated?

 

[kams1973]

The belt is slipping on the motor pulley?

 

[dodge610]

Have you checked the start up capacitors in the motor The guy next door had almost the same problem found out one of his capacitors was bad.

 

[firebox40dash5]

Have you checked the start up capacitors in the motor The guy next door had almost the same problem found out one of his capacitors was bad.

That would be my thought, though the "run" caps, not the starter, if applicable. IIRC some motors with run caps will physically run when they go bad, but they run like ****.

I'm not sure the check valve *should* affect it like that, I'd think it would be pretty much open as long as the compressor was pumping. I know the compressor at work had a stuck open check valve when I got it running. It would get up to pressure just fine, but as soon as it cut out it would bleed down the tank through the unloader valve until it dropped down to cut-in pressure.

 

[bsaint]

When belts tensioned properly, I can't remember a time that the belts would slip before the motor tripped off on high current.

 

[gregwils]

I probably didn't fully describe what is happening as it poops out. Yes, the belt is starting to slip. As the air pressure builds in the compressor, there is a very faint squeal that starts and gets louder and louder if you let it run. I usually shut it down. The motor doesn't sound like it is giving up, the belt is getting the short end of the stick.

There is about a 3/4 of an inch of deflection in the belt. However, I can't force it to slip by hand no matter how hard I pull. If you start the compressor when the tank pressure is 60+, the belt slips on start-up. Sometimes the belt gets traction, sometimes it slips depending on how much pressure is in the tank.

It doesn't seem like the motor is weak since the belt is slipping. I have no idea where the start-up capacitors are located.

Thanks.

 

[RCStocker]

Before I would do anything get some belt dressing and spray the belt. If the belt is old it will get hard and slip. Belt dressing makes it grab. I used it 40 years ago on things and it worked well. I don't kmow why I stpped using it other than none of my belst have sliped sense I have been her in warm Southern California. I have more problems with a little belt slipage on the farm in Indiana where it gets cold and damp.

It might be the moter not getting enough torque on start up but I think the problems is in your compressor head. It sounds like there is a lot of ware and slop binding it up.

 

[71goldss]

No compressor expert here, but from your description it reminds me of a hydraulicing cylinder on a combustion engine. I don't think that's possible on an air pump unless there's a massive oil leakage past the rings. I'm sure you'd be aware of that and it's probably still not possible anyway.

 

[kams1973]

Let's back up a bit. You stated you replaced the pressure switch and the belt. Were you having any trouble prior to replacing these items? Also, belts come in different widths. Are you sure you have the right size belt for your pulleys? If it is indeed the correct size, tighten the belt and try again.

 

[gregwils]

Yes I was having issues at the beginning, when the squealing problem started my first step was to replace the belt. I did so with the original part #, so I believe it is correct.

I have to stop for today, but will tighten the belt a little more tomorrow AM and post the result.

Thanks everyone.

 

[firebox40dash5]

Yes I was having issues at the beginning, when the squealing problem started my first step was to replace the belt. I did so with the original part #, so I believe it is correct.

I have to stop for today, but will tighten the belt a little more tomorrow AM and post the result.

Thanks everyone.

I will say I had to tighten both belts on mine a lot more than I thought was going to be required. Like 42" prybar in the motor slot prying the motor tight. Add more if it's only 1 belt.

 

[bsaint]

3/4" is too much. Deflection needs to be like a 1/4" or so with moderate pressure.

 

[daviomaron]

The guy next door had almost the same problem found out one of his capacitors was bad.

 

[Jagmandave]

Are you sure it's full of oil?

I changed the oil on my compressor and the oil level window was stained and I thought I got it full, but didn't and galled the bearing slightly. I took it apart and cleaned it all up and it's been fine since, but I thought sure it was a gonner.....

 

[Fixnair]

Remove the guard and run the machine. When the thing starts to slow down take a piece of smooth wood,like a hammer handle, ans apply pressure downward on the belt. Careful here. Be sur you press in the middle uf the belt span and do not have any loose clothing or long hair. If the thing speeds up then the belt is loose.

 

[dodge610]

Could the key way on the motor or the compressor itself be sheared off and be slipping that way check both key ways.

 

[gregwils]

Case closed. It was the belt. I probably misdirected many comments by my early claim the belt was properly adjusted. This time I got some leverage and maintained pressure while I tightened the belt. There is still some deflection in the belt, but far less than before.

I can't thank you all enough. Great forum.

PS - I noticed there were nearly 400 people logged in this AM and another 200 guests. I guess there are a lot of us tool lovers out there. Thanks again.

 

[dodge610]

NO problem gregwils thats what all of us hang here for to help each other out. OH yeah and to get our fixes and buy more tools.

 

[bsaint]

Great to hear! Glad we could help.

Note - I called belts first