Hitachi builds a very nice compressor, however suffers from the same problem that all brands will eventually encounter. Failure of the pressure switch. The pressure switch is a very hard working component
of the unit. Depending on use, the pressure switch may cycle from as little as two or three cycles a day to as many as dozens per hour. The pressure switch has springs, contacts and unloader
features that eventually wear out. The two most common failures are the contacts and the rubber diaphragm
that acts against the springs to shut the unit down. Sometimes the screws securing the base of the switch the inlet port come loose and cause the problem that you are having. (The rubber diaphragm is between the base inlet port and the switch) Simple test is to spray soapy water around base of switch to check for leaks. Replace the switch as necessary with a SquareD brand available at www.grainger.com
instead of factory unit to save money and increase life. You may have to make simple modifications however the money saved will be worth it. Choose a pressure switch with cut-off range between 120-139 psi. The higher the cutout switch setting you choose the shorter lifespan for your compressor. Your compressor works harder and gets hotter when achieving higher pressures. Try to use either no extension or shortest cord possible to max life of unit and compressor oil instead of motor oil to prevent carbon deposits. Good luck and email if you have questions about your Hitachi.