125 psi sears air compressor only goes up to 40psi and will not stop running I've replaced pressure switch and manifold.

This could possibly be, you have some water from condensation buildup inside the tank, liquid does not compress. Before this next step make sure the tank is to 0 psi! Now, there should be a relief valve Wingnut on the bottom. Loosen the wing nut and drain as needed. Then retighten the wingnut (Do not overtighten). Plug the compressor in and try it. My second suggestion is, the psi adjustment pressure knob could be faulty replace as needed!

maybe you are reading the gauge wrong
the tank gauge and the regulator gauge will read the same but the gauge that reads when you adjust the regulator is the out line pressure to be n maintained during tool use

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.

I've a ingersoll compressor ssr ep 20 which is shutting down on high airent temperature.

Hello;
150 is your cutout pressure. It's the factory setting and is not a problem. But, It appears you have a pop off (safety) that is set for 125 psi, So, If you want 150 psi, the pop off needs to be adjusted. If you want 125 the the cut out switch needs the adjusting. The setting. More than likely the 125 psi pop off valve is correct and the switch needs to be adjusted down below the pop off pressure. To sdjust the switch, remove the cover of the box the cord comes out of.Adjust using the screw(s). There should be one for cut in and another for cutout pressuressures. The cut in pressure should be 90 psi and the cutout should be at 125 psi.If the pop off valve blows off at 125, It needs either replace or adjusting. It's best to replace it.since the spring inside has lost tension. You will be constantly adjusting it otherwise. Good Luck -Ned_ Take caution not to get your tool or fingers into the electrical in the switch box.

these small compressors do not have a long life especialy if they are run for more than 15 min /hour , bet no body told you that when you bought it the ones with an iron barrel are better so to problem
1 piston rings worn or broken / replace
2 daft i know but air leaks/ when it is running you carn't hear a leak cos of the running noise,run it up as high as it will go switch off and listen /repair leak
3 sticking or passing valves , these are located in the cyl head /take filter unit off,run it when it comes up to 40 psi put your hand close to the inlet port if the inlet valve is passing you will feel a sort of chuff chuff on your hand ,switch it off ,if you can hear ,and feel air coming out of the inlet port the Exaust valve is leaking ,sadly these small comps are difficult and bloody expensive to get spares for"they want you to buy another one " so depending on the amount of use it has had it might not be woth while repairing hope this has been of some help
merlin v12

look at he check valve

I have worked on many makita compressors and have run-across this problem on a few of them. Your compressor has a check valve that is supposed to hold tank pressure after the switch reaches set pressure. There is an unloader valve built into the pressure switch that releases the pressure in the discharge hose after the unit shuts off. The unloader allows the compressor to restart with-out any pressure in the discharge line. If the brass check valve is leaking pressure back into the system, air will leak out of the unloader valve. Follow the discharge line to the tank and you will see the brass check valve. To test valve for fault, run the compressor till it builds around 80 psi and unplug the unit from the wall outlet. Remove the 1/4" hose connector from the check valve and check for air leaking out of the valve. If it is leaking you can order form www.toolpartsdirect.com. or call the makita 1-800 number. The price is about the same. Good Luck on your repair.

My air compressor builds up to 40 psi and just keeps running, i have a craftsman 5 GAL, 1HP, 125 PSI and pressure goes up to 40 psi and dose not go any higher and on the other hand engine keeps running and dose not stop. Please advise?
Thanks.
Kia

does the compressor keep running all the time but never gets above 40 or does it turn off at 40?
if it is turning off at 40 I would try using another gauge just to be sure it is 40psi, and if that is the case then you probably have a faulty pressure switch, if the compressor is constantly runnign but won't get past the 40psi then you may have a worn out compressor, check the oil for either a low level or if the oil is dirty, if it is you may just need to drain and refill but if that doesn't fix the issue then you will need to rebuild the compressor