AIr Compressor Question


New Member
Nov 5, 2020
Washington State
We recently were given an air compressor for free. It's been a good little compressor but it has had its moments.

A few days ago we were using it and it began to struggle to reach pressure to the point where it stalled and no longer would turn over. After looking at it again a week later the compressor fired right back up with no complaint and got the tank back up to125 psi. We were concerned that a lack of maintenance may have lead to it seizing. This doesn't seem to be the issue as the compressor can be turned by hand pretty easily. I am now suspecting that the motor may need to be looked at. I have been reading that the capacitors can go bad and may be in need of being replaced. Actually more notably, we were naively running the compressor off of an relatively thin gauged extension cord. This may be the real issue. Feel free to make suggestions I'm all ears.

Also while looking the compressor over and observing how it works I came across a line that runs from the base of the control box and delivers main tank air to the top of the cylinders of the pump. There is a ball valve present as well so its been running with line off. I have tried digging around for a manual that names this line but haven't been successful in my search yet. I was curious if there may be a knowledgeable person that could explain its purpose. I have attached an image with the line circled as well.

Link to the compressor:

Many thanks.

After looking closer at the other forums to post in I realized that this isn't likely the correct one. After looking into how to delete a thread it appears I am unable to? If a moderator would like to move my post to the correct
thread (such as DIY and General non-hearth advice?) please feel free to.

compressor.png IMG_20210111_172526911.jpg IMG_20210111_172538421.jpg
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Minister of Fire
Dec 19, 2009
West Michigan
You're on the right track for sure. It takes some pretty big starting amps to fire that compressor up. Try the shortest run of the heaviest cord you can get on it. As long as the oil's good, next thing I'd look at is the cap. Be careful with the cap, don't get shocked, look up capacitor safety, testing, etc.. if you start messing with the electrics.


Moderate Moderator
Staff member
Aug 2, 2006
Northern IL
From your pics I can't really tell, but I can pretty much tell you that the small pipe is either a pressure relief for the compressor head or it is the line that feeds the pressure to the regulator for on/off switching.
Chances are it is a relief valve. It only affects startup, not when it is running.
Plug the unit directly In to a wall outlet and see how it acts. It is not real common to need a cap change.
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Feeling the Heat
Aug 17, 2014
Perryville, Mo
On those portable style like that with a gas engine, there was a small lever you flip so it wont build pressure while starting it. Not sure if the electric has it

Bad LP

Minister of Fire
Nov 28, 2014
Northern Maine
NEVER EVER use an extension cord on a compressor unless you absolutely have no other options and if you must it should be nothing less than a 12Ga cord and only as long as you need it.

Air hoses don't have a voltage drop issue. You can always run a larger diameter feeder hose to a manifold then branch off from there. AC motors are not cheap.