Help diagnosing compressor

[hondaman900]

I just picked up an old Sears Craftsman 20Gal 1.5hp 110V compressor. The motor never shuts off, and it keeps pumping air until the relief valve blows at about 155 psi and keeps going. There's a small metal tab under the small air line from the compressor head that activates the contacts in the pressure switch (see pic below). I can manually press that up and it stops the motor and holds until the pressure drops to about 100 psi and then it kicks in and starts the motor again, but doesn't stop again when pressure builds. I'm thinking I need a new pressure switch, but wanted to check here in case it's something else or if someone has a better diagnostic approach that would help. Any suggestions? The compressor is Sears model 106.153980.

Thanks in advance

Heres' the compressor:
http://lh5.ggpht.com/_wJHoEnrxghE/SpS2X-apiSI/AAAAAAAADL0/HGOEMptJO8M/s800/20090825_11.JPG

Here's the pressure switch tab I mentioned:
http://lh3.ggpht.com/_wJHoEnrxghE/Spn0q5O6-1I/AAAAAAAADPA/6li63PFWpUQ/s800/20090829_4.JPG

Here's the pressure switch, opened to take a look. The on/auto switch is missing:
http://lh4.ggpht.com/_wJHoEnrxghE/Spn02cAtEfI/AAAAAAAADPE/waPts247FkA/s800/20090829_5.JPG

[bgott]

That valve on the small line that is triggered by the lever coming out of the pressure swich is the unloader. It relieves the pressure from the head so the motor can start the compressor. You need a pressure switch.

[Thedroid]

You can take that pressure switch apart, clean everything up, reset the on/off setting, and try again. I was brought a compressor with the same switch and same problem about a month ago, and I did the above to it. It's working like a champ now. Only problem is, those switches are very tough to get back together. It's worth a shot, because a decent pressure switch can cost quite a bit.

[hondaman900]

Thanks guys.

Thedroid, how do I reset the on/off setting? Is it obvious when I get in there?

[hondaman900]

Okay, I took off the pressure switch. It's a Furnas CW-2075-09 rated to come on at 120 psi and stop at 150 psi.

http://lh4.ggpht.com/_wJHoEnrxghE/Spsb1Fs4mfI/AAAAAAAADP4/y0d9pbXE89w/s800/%21cid__SNC00094.jpg

I had thought that there was a leak in the connection where the main compressor line enters the manifold. You can see the messy red RTV gasket material the previous owner used on it. I took that apart yesterday, cleaned and sealed it well, and left it overnight to cure. Today I fired it up and was surprised that it still leaked. On closer examination, the leak isn't coming from the manifold (the escaping air was just deflecting off it) it was coming out of the underside of the pressure switch. There's no port or opening for it to come out, so I'm not sure where it was leaking from. The leaking would stop if I reduced the pressure in the tank to about 100 psi.

I used WD-40 on the contacts and gave them a good workout, but no difference in the switch operation. It uses security star slotted head bolts to keep the switch mechanism together so I'll have to get that tool to dig deeper.

Given that the switch itself is leaking and the on/off/auto switch is missing I'm thinking perhaps the switch is not salvageable? Thoughts?

[Thedroid]

The adjustment screw is located right above the black and white wires in your pic. It's the slotted screw. You could try to go all the way out with it, and then back in to your desired pressure. If it's leaking then you might be better off getting a new one. If you take it apart, then you can look at the diaphragm to make sure it isn't ripped. If not, you might be able to clean it up and put it back together with no leaks. Just be warned, the mechanism is tricky to get back together.

[Thedroid]

If you decide to buy a new one, I like the Square D. I'm not sure if Allen-Bradley make those type, but if they do then thats my recommendation.

[hondaman900]

Thanks. I got a Square-D replacement unit, single port, 120/150 110V/220V with switch and unload valve on eBay for my "best offer" of $12. The port is female thread on the new one and mine is male, so I'll have to do a little plumbing - no biggie. That should rectify the issues.

I'm thinking while I have the parts off it I may degrease, sand and paint it. If I do I'll post pics back here.

Thanks for all the help. I think it's close to resolution.

[ImportTuner]

Sure don't look like any Craftsman compressor I've seen. How do you know it's a Craftsman ??

[hondaman900]

Eh, because it's labeled as a Craftsman......here.....

http://lh5.ggpht.com/_wJHoEnrxghE/SpS2Dys9mmI/AAAAAAAADLg/SvNswy3U0as/s800/20090825_6.JPG

and here....

http://lh3.ggpht.com/_wJHoEnrxghE/SpS17PX6PNI/AAAAAAAADLU/2J0N0lJE5R8/s800/20090825_4.JPG

Apparently this model was manufactured by Campbell Hausfeld and also sold under Speedaire and Craftsman brands. From the tank stamping, looks like it's 1964 vintage.

[ImportTuner]

Wow, 1964 vintage .. nice; didn't own a compressor back then. I was using a Monkey Ward electric impact ..

[hondaman900]

Hah! yes, it's old. I wasn't using a compressor back then either. I was two and using a pacifier :)

It's in pretty good shape for its age, maybe better than I am.

[SSFOS]

By chance anyone think they can identify this compressor? Or tell me if there are any casting marks to identify the model number of the compressor? :headscrat

[jarhead]

SSFOS, that appears to be a "speedaire" compressor pump.

Mine looks the same as yours. It could be a Dayton made for Sears or Grainger. Try googling 106153780 and check out the Sears link. I would be interested how the filter screws in to the top of the head as mine just has a cloth filter.
Thanks, Joe