Pressure in the tank only builds to 30 psi

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

Most likely in tank check valve is leaking or belt is slipping. Belt tension easy to check, should not deflect with thumb pressure. Check valve should not let air escape out of tank. Easy to check. Run compressor till pressure builds to around 50 psi. Then unplug machine from power outlet. Listen for air leaking out of tank. In bad cases, air will actually leak out of intake filter. Replace check valve as needed. Good luck

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?

The pressure regulator on an air compressor is designed to let the pump motor run until the pressure in the tanks reaches their safe level. While you are using the air the pressure drops in the tanks until it reaches the level where the pressure switch turns the motor on again and refills the tanks to their rated level. The pressure where these two things happen is usually with in ten psi above or below the rated levels because few regulators are so precise and are affected by temperature that they turn and off exactly at the rated pressures. If a pressure regulator is damaged or broken it is possible for the tank to either reach unsafe high levels or not turn on when the pressure drops to where it should restart the motor. If you are in doubt, have the regulator checked or replaced as overpressured tanks are very dangerous.

When the regulator fails, usually air will leak from under pressure knob, however in your case the nut must be stripped of its thread. May need to replace the manafold for fix(most regulators are built into manafold). To allow you to continue using the compressor, add another quickconnect at pressure release port. Let all air out of the tank. Remove pressure safety release, and install tee fitting. Re-install pressure safety on one of the ports of the tee fitting and a quickconnect at the second port. You will have tank pressure available while you order the manafold. Or just add a generic regulator before the quickconnect and forget about replacing manafold. Good luck.

The problem with compressors not building pressure is usually a bad pressure switch or bad regulator. Does the motor shut off at 20psi or does it continue running and not build pressure? If the motor continues to run with no increase in pressure, the you should go over the machine looking for air leaks from your regulator back all the way to the motor. Any air leak while the compressor is running can cause the pressure to "peak" way before the intended shutoff that it is regulated to.

Sounds like a pressure switch to me. I would like to ask you a few more questions, let me ask you this, is the tank set at 60 Psi or the regulator? You can email me at [email protected] for faster response time.

The most likely problem is a burned out "run capacitor" on the motor. If you continue to try to run your compressor in this condition it will burn out the "starting capacitor" and/or motor as well.
It's also possible that you have a bad start up pressure relief valve, this valve will be between the compressor and the tank. If this valve is working properly you should hear a hiss of air as the compressor motor shuts off.
A reasonable motor repair shop should be able to replace the run capacitor for $20-$50 plus inflation, depending on your area.
If you need to test the start up pressure relief valve, you need to take it loose at the compressor or tank. Just loosening the line may not work depending on the style used. Note: sometimes just taking this loose to test it causes you to have to replace the valve.

if it is lifting both valves I would say that the pressure switch (regulator as you call it) is defective, if you try to shut it off using the manual switch and it keeps running, I would say that the switch is welded shut. if it does not shut off by 125 psi then it is faulty. The pressure switch is what controls the motor in response to pressure in the tank.