My compressor doesn't build enough pessure.

https://www.google.com/search?q=Northstar+Gas+air+compressor+M459392C+continues+to+build+pressure+even+after+idle+down

1. Pressure switch: The pressure switch may not be shutting off the compressor when it reaches the set pressure level. If this is the case, the switch will need to be replaced.
2. Check valve: The check valve prevents the compressed air from flowing back into the compressor pump when it is not running. A malfunctioning check valve can cause pressure to continue to build up, even when the compressor is idle. A damaged or worn-out check valve may need to be replaced.
3. Piston rings: If the compressor's piston rings are worn or damaged, air can leak past the piston and cause pressure to continue to build even when the compressor is idle. In this case, the piston rings will need to be replaced.

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Most compressors that come into the shop are not reaching cut off pressure. Here are a few tips on determining the problem /s. Three problem areas. Leaks,valves/head gaskets or worn cylinder/rings. Leaks on small compressors are easy to find by spraying soapy water on all connections and drain valves. Also spray on head gaskets. Repair as needed. No joy? Continue with checking valves. Most small compressors have reeds for valves and fail quite easily. There should be good suction at intake opening. Run compressor till no more gain in pressure. With air filter removed and pump running feel for suction at intake. If you feel very little suction or air blowing out of intake , most likely bad reeds or gaskets. If you feel good suction however no gain in pressure then likely worn cylinder. Good luck with repair.

Hi, There are different posibilities. I would need more information. Was it always like that? Does the guage on the main tank and the guage on the regulator both not show more than 20psi? When the auto shut-off is triggered do you feel there is more than 20 psi in the tank?

Might be the valve plate is worn or has a broken reed.

Your concern is very well placed, at pressures that high a lot of damage can be caused by a failure. According to the manual for this model air compressor the approximate cut-in pressure is 160 psi and the approximate cut-out pressure is 200 psi. Meaning it should pump up to 'about' 200 psi and shut off and not come on again until it gets down to 'about' 160 psi. They say approximate and I say about because it's not an exact science setting the pressure switch. Spring rates are not always exact, pressure guages are not that precise, etc. When turned on, it should shut off at 200 psi +/- 10 lbs. If it goes more than 10 lbs over that (220psi), I'd recommend you get the pressure switch and or guages checked or replaced.

The check valve is not holding the pressure back off the head,therefore allowing the pressure to build up fully.

Are you sure the gauge is relaible??

If so then a valve in the compressor is allowing leakage.

Check to see if air is leaking past 'pressure relief' valve. It's probably leaking and that's where all the air is going.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

sounds like the regulator is fualty.

Does the compressor continue to run but not build more pressure? In which case it is an air leak most likely, or does the compressor shut off at 50 PSI? In which case it is mose likely the pressure switch. If it is an air leak you can un-screw the guage and coat with putty or teflon tape and reinstall to clog the leak around the threads..