20 Most Recent Hitachi EC89 4 Gallon Twin Stack Air Compressor Questions & Answers

2 things The check valve on the tank will not close for 100% rust parts from some metal parts in the pressure pipe metal rings can be used and give problems over time , or under voltage on the power group. are sometimes things that are hidden and not seen .

This is a really hard question to answer - not in the owners manual or elsewhere on the Internet. I think I did find the answer for future reference for other people with the same question. The parts depot for this model of compressor list a 8oz bottle of oil so that should be the maximum amount of oil to put in. Also on the subject of oil please note that this compressor uses 5W50 synthetic oil. If you use regular oil your going to have all kinds of grief with it not starting easily and causing a lot of wear on start up.

I dont know what it cost new, but I dont think it cost as much as you are thinking. Here is a parts list an exploded diagram to replace parts. If the part is cheap enough then here is the link to it. Hitachi EC89 4 Gallon Portable Twin Stack Air Compressor Parts

check valves on the head of compressor

Several things to check. Check amp draw with meter to make sure that the reset is not bad. It amp meter is showing low amp draw when it trips, then replace reset. If reset is good check condition of the cold start valve. The valve will not allow pressure to build until motor is at full rpm and the pump is making good pressure/volume. If cold start valve does not close, check pump for leaking or broken reed valves. If cold start valve is good, check the capacitor for at least 10 percent of rated valve. Low pressure /volume is usually leaks from tubing or leaking /broken reed valves or burned gaskets in the head of the pump. Finally, make sure that the check valve or non-return valve is not leaking pressure from the tank causing back pressure. Good luck

The air is leaking from the check valve. Follow the air discharge hose from the compressor to the tank. The brass or chrome fitting at the tank contains a one way valve that most likely has debris between seat and valve. Remove the valve and clean or just replace with new. Parts are available at www.toolpartsdirect.com. Good luck

The early Hitachi EC89's came with a 40 microfarad capacitor to start the motor. This is insufficient when its cold, or the compressor hasn't been used in a while, or the compressor is still in its break-in period. Hitachi later changed it to a 60 microfarad capacitor, as it now is with the currently offered EC89's, which provides reliable and consistent starts of the electric motor. FYI: the capacitor is the white tube looking thing just under the black cover on the top side of the compressor. You can just see it without disassembling anything if you peek under the black cover to the best of your ability. To get at it you need to remove the black plastic cover. To do that, it takes about 20 minutes of disassembly time and a few tools: unplug the compressor, disconnect at least one end of the copper pressure tube (the tube that runs from the pump to the tank), remove the four main bolts that hold the black steel compressor base to the main frame, now you can get at the four phillips head screws that hold the plastic cover on, loosen (but don't remove) these four phillips head screws, then pop off the plastic cover (there are anti-vibration side locks that need to be disengaged- by using a long flat head screwdriver from the inside- to pry them and pop them off from the inside). Once the black cover is loose, you will either have to reach in and disconnect the two wires to the breaker, or unthread the breaker's little hex nut and separate it from the black cover. Replacing the 40 microfarad capacitor with a 60 microfarad capacitor (available at your local electric motor rebuilder- yellow pages) will resolve the problem of the weak starting motor that pops the breaker before the motor gets a chance to start rotating. Shame on Hitachi for not publishing this fix themselves.

Order a new dipstick it could have a plugged vent or a bad o-ring. they're not very expensive if you have a local service center. If not try mastertoolrepair.com or toolpartsdirect.com

Its your reset button on the compressor that's bad! I have the exact same compressor (EC89) and it did the same thing! Compressor would run great for 15-20 seconds, then trip the reset button. I ordered a new reset button off e-bay, replaced it, and it works fine now. Good overall compressor! but has cheep china electronics installed. just replace the reset button and you will be good to go....cheep fix!!!

Several things to check. Amp draw to be within number on plate, if amp draw not correct check capacitor, should be within 5% of rating on cap.. If amp draw about right and cap reads good suspect faulty breaker. If amp draw high and cap. good check for leak at in-tank check valve. With pressure in tank remove hose at check valve spray soapy water. If check valve good, suspect reed valves leaking. If reeds are leaking the compressor will take longer than normal to fill and the discharge tube/air will get very hot. It is recommended to note the amount of time it takes to fill tank when unit is new and compare this as unit wears. Length of time to fill is an indication of how well unit is working. A combination of leaky valves and leaking fittings as well as leaking checkvalve will cause motor to overheat.

IF it is building up to the correct pressure then the pressure switch has malfunctioned. The part number for a new switch is 160580.Parts and owners manuals are located at this link near the bottom of the page;Hitachi EC89

There is a small notch on the dipstick. Your oil level should be in that notch.