The pressure regulator can easily be replaced by removing the large plastic decorative cover. The manifold behind the cover is the part where the regulator , gauges, and quick connects are attached. The manifold is fed air from the pump via a plastic hose connected to the pressure switch. The regulator sells for about fifty dollars. This part usually fails in two ways. It leaks air from the knob or no air pressure will reach the quick connects. If your problem is no air at the quick connect, you can do a temp repair by removing the safety valve and installing a tee fitting at the port. On the tee fitting reinstall the safety valve and a quick connect on the other fitting. This will give you tank pressure . Good luck.
SOURCE: ec12 hitachi air compressor will not build
most likely the the reed valves are stuck or miss aligned. Worse case senerio your piston seal blew causing this not to build pressure. Read manual on how to disassemble head. to remove should be 4 bolts and your copper line, just be careful of the reed valve plates, they are thin steel that sit into the head. Put back the same way you took it apart.
SOURCE: starter valve dont close hatachi ec119sa (air compressor)
The start valve gives your motor a running start before the motor begins to load as the pressure increases from an empty tank. The motor strain is more profound when there is pressure in the tank. If you plug the valve, the motor will instantly encounter a heavy load because it has to force air into a partially filled tank. This extra load without the valve will shorten the life of the capacitors and motor windings. There could be two problems with your unit that can revealed by test. What actually closes the valve is a certain volume of air produced by the compressor. If the compressor is not pumping to full efficiency or there are leaks in the discharge hose the valve will not close. Or the valve is faulty. With an empty tank, plug the valve and run compressor and test airline for leaks with soapy water. If no leaks, empty tank of air and restart compressor and take note of the amount of time it takes to fill the tanks to shut off. If it takes an unusually long time to fill, then the compressor probably has valve problems causing low air volume. If the compressor fills to shut off in a short time frame as compared to a similar model then replace the valve. Leaking valves in the head will also cause the pump and discharge tube to run very hot. Parts are available at www.toolpartsdirect.com Good luck with your repair.
SOURCE: Hitachi twin stack problem.
You stated that the compressor started up fine. I'll assume it reached it's max psi then cut out. Then upon reaching it's cut-in psi the motor ran slowly for a few seconds, then kicked off. I also assume you mean check valve when you refer to the non return valve.
If this sounds about right then. The first thing I would do is bleed out all the air from both the tank and the pump supply line leading from the pump head to the tank's check valve. You can do this by simply loosening the fitting that attaches the line at the head or the check valve. Once done try running the compressor again.
The purpose of this is to check the unloader valve. This valve bleeds off the pressure that remains in the compression cylinder and the supply line up to the check valve. When functioning normaly it will bleed off this pressure once the motor shuts off. If it is not working correctly then when your compressor starts back up (once it is already been filled) the piston will be working against a psi close to the max psi.
If the problem reoccurs only after the compressor has reached it's max psi, then the unloader valve is most likely the problem. If however it will not start up at all even after a complete bleed then it has to be something internal to the pump and\or motor.
Please try this and let me know (or repost) your findings.
If it's the unloader valve I should be able to explain how to repair this valve.
Good luck.
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SOURCE: do not have manual for hitachi ec12 air
You have to manually adjust the pressure regulator. Make sure drain is completely closed. The one thats on the bottom of the tanks
SOURCE: Hitachi EC 12 Air Compressor does not keep pressure
to repair this problem (a) the pressure switch is not working,(b) check valve or non return valve sticking(stripe down repair and refit)
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