My compressor will not pressurize over 25psi. Motor balks and shuts off after 2 minutes.

by Anthony G
(Santa Cruz, CA)

I just got this old Craftsman compressor from my neighbor who was getting rid of it so took it and am trying to fix it. It been outside for a year. I've cleaned it up and put in fresh oil, cleaned the motor etc.

Its a 220 volt, 2HP, twin cylinder, 150psi, 20 gallon tank model 106154780.

When I press the reset button it will start and repeat the same process.

I don't know what is wrong with it as I am not very well educated re these machines. After reading you faq's, I was thinking possible pressure switch is bad and or the check valve is dirty. I've run it for longer periods with the drain cock open and no problem with the motor overheating. I've disconnecte both of the tubes exiting the head at top of twin cylinders and air is pumped out of both so it seems the pistons and inlet and outlet valves are functioning. Where is the check valve located? I think I should check and clean it as one of the first things to do. Thanks for any advise you can provide, I would really appreciate you expert advise on possible trouble shooting tips you might have. I've included some pictures of the unit. One more note, the previous owner said he stopped using it a year ago because it would stop working after reaching about 40psi. I don't know if that helps. Anthony

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Bill says...

Anthony, it doesn't sound to me like it's a pressure switch issue. If the pressure switch wasn't working, your air compressor wouldn't turn on. The pressure switch is set to turn the compressor off at 130 PSI or so (depending on the type of compressor and switch settings), so, since your compressor doesn't reach the high pressure cut out, you really don't know if that setting is working or not.

Go to the troubleshooting section, and click on the pages about why a compressor won't build pressure.

I suspect, since your compressor sounds like it works well without load, that it's either a pump problem or the motor may need rebuilding or replacing.

Re: "the previous owner said he stopped using it a year ago because it would stop working after reaching about 40psi" which sounds to me like he had it diagnosed and it was too expensive to repair, so they dumped it.

Also, go to the Valve page, and click the link for Check Valves to give you info on those.

Good luck.

Bill