Reason: Piston ring is damaged，
Cylinders are scratched, worn or not smooth，
Air flow has been restricted recently, too much oil in the crankcase,
The lubricant grade is incorrect.
Action: replace with new piston rings
Replace with new cylinder
Clean or replace the air filter and check for other throttling at the air intake end
Drain to proper oil
Use the correct grade of lubricating oil
Reason: The pressure switch did not cut off the motor
Action: Manually operate the pressure switch and place the disconnect button in the OFF position. Replace the pressure switch if the motor still runs.
Reason: low oil level,
loose bolts or nuts,
The motor belt is loose,
The compressor pulley is loose,
The valve plate is damaged or loose,
Worn or unbalanced connecting rod, piston pin or crankshaft bearing, main bearing.
Action: Check the oil level and keep it at the specified level,
Check all bolts and nuts and tighten as necessary,
Tighten the pulley bolts,
Check pulleys are in place and tighten as needed,
Check the valve plate, clean or replace as needed,
Check all parts and replace as needed.