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Compressor Troubleshooting

Lionclaw

Lionclaw

Well Known Member
I have an old Sears oiled air compressor that has been serving me quite well until a few days ago. The motor buzzes but will not spin. I thought for sure it would be the starter capacitor. I ordered a new one and just finished installing it, but no go. It still buzzes. It isn't locked up. I can spin the drive assembly by hand. If I turn it on and spin it by hand a bit I can get it running. I tried bypassing the pressure and power switches and get the same problem.

Anyone have any ideas?
 
It could be the starting coil switch contacts. There's a centrifugally- operated mechanism on the rotor that closes the start switch when the motor is stopped and opens the switch when the motor starts spinning, kind of like an impulse coupling on a magneto. Chances are, the contacts are dirty, corroded, or worn. Take apart the end of the motor that has the switch and clean the contacts with emery cloth or a fine file. While you're in there, oil the bearings, too.

Heinrich Gerhardt
 
Wow, thanks for the quick response Heinrich.

I pulled it open and found what you described. It was quite dirty. I cleaned everything up and filed the contacts. Reassembled and get the same problem. One thing I did notice was the casing around the breaker inside is broken. I'm not sure where I can get another, or if it would be a good idea to bypass it. I'll pull it apart again and see what's going on there.
 
When I unscrewed the breaker from the rest of the casing the breaker just fell apart. The plastic housing is in several pieces. Inside it has a resistive element and a small pop disk. As soon as I figure it out I'll try bypassing it. If that works, I'll try to source a replacement. I figure there's no point finding one until I know the motor still works!
 
Unfortunately bypassing the breaker didn't help. Still buzzing and only sort of slowly turning.

I'll play around with it some more tomorrow. In the mean time if anyone has any advice please feel free to chime in! :)
 
Was there any change with the electrics? My compressor sometimes acts like that when I use a long extension cord but does fine when plugged in directly.

Mario
 
No change in electrics, although that is a good thought. I've had the same problem with extension cords in the past. I tried plugging it into a different socket on another breaker just for good measure, and get the same result.

I'll tear it down one more time to play with the centrifugal mechanism a bit more. Definitely a bummer, but I may have to try and find another motor.
 
I pretty much gave up today. I'm thinking it must be a bad startup winding (although I may tear it down one last time to check). Local motor shop wanted to sell me a new motor for $140, and I'd have to modify the mount to make it work.

I'm thinking about buying the husky 26gal compressor from Home Depot. Didn't really want to spend this much, but I might as well get a good one.

http://www.homedepot.com/webapp/wcs...langId=-1&catalogId=10053&productId=100063473

Anyone have any thoughts/opinions?
 
Hmmm. The breaker controls power to the main winding AND the start winding, so if you get anything, the breaker is working. I'd check both windings with an ohmmeter at this point.

You can get motors from Harbor Freight. http://search.harborfreight.com/cpisearch/web/search.do?keyword=motor. That's what I did when I got a 2-stage 3-phase compressor for free from a friend.

My only advice about compressors is to avoid the oil-less direct drive ones. The quality of the noise they make is awful. Really annoying to my ears. Belt drive, oil-type is the only way to go.

Heinrich Gerhardt
 
When it comes to compressors...

When it comes to compressors, call Graingers, they have and know most everything for most makes and models of compressors.

They are always reasonable.

With most places you get what you pay for, or less.

With Grainger, you will get what you pay for or more.

Their SpeedAire New and replacement parts have always done well for me.

If you've got it spend the bucks and get something you wont have to fix, only maintain.:cool:
 
GAHco said:
When it comes to compressors, call Graingers, they have and know most everything for most makes and models of compressors.

They are always reasonable.

With most places you get what you pay for, or less.

With Grainger, you will get what you pay for or more.

Their SpeedAire New and replacement parts have always done well for me.

If you've got it spend the bucks and get something you wont have to fix, only maintain.:cool:
Click to expand...
Ditto's on this advice. Industrial-type supply places like Grainger are almost always preferable to consumer type places like HF or Sears when you need parts or spares 'down the road'.
 
Electric motor repair.

I am in the electric motor and pump business in Houston. Deal with this everyday. E-mail me if you still have questions. I will e-mail you back my 1-800 number. That round black plastic thing is a thermal overload. I can order you one if you can get a number off of it. Yes you can tie all of the wires going to the overload together and the motor should run if nothing else is wrong. Will need more info to go any farther. There are some replacement motors for your Sears compressor. Sounds like you have one that has a special base that pivots on one side and tightens down on the other to adjust belt tension. Some people just knock off the ears that stand up on the base and put a standard motor on and drill holes to mount it. Hard to adjust belt tension that way though. Let me know if I can help.
DWC7A
Dennis Conner
[email protected]
RV7A Working on second wing
quick build fuse in hanger
 
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