Question about Hitachi EC89 4 Gallon Twin Stack Air Compressor

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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

Posted on Mar 24, 2014


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Hitachi EC89 air compressor just hums and reset button pops..doesn't turn on at all..

it indicates that the start / run capacitors are failed
remove the power lead from the wall and get the details from the capacitor/s and go to a motor rewind shop and they will have replacement capacitors available
if you can take the capacitor/s with you it is even easier

Oct 26, 2015 | Hitachi Air Tools & Compressors

2 Answers

I found a ec89 , 9/10 at a pawnshop for $50 , BUT it dosent build pressure. How much would ya guess to repair it and good buy or stay clear? Thanks

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

Jan 28, 2015 | Hitachi EC89 4 Gallon Twin Stack Air...

1 Answer

Htachi ec89 Thermal Protection trips

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!!!

Sep 01, 2012 | Hitachi EC89 4 Gallon Twin Stack Air...

1 Answer

Hitachi ec89 will not shut off

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

Aug 19, 2012 | Hitachi EC89 4 Gallon Twin Stack Air...

2 Answers

Very hard to start when cold, even in temps above freezing but below 60 degrees.

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.

Feb 27, 2011 | Hitachi EC89 4 Gallon Twin Stack Air...

2 Answers

The overload keeps tripping

I have had a Hitachi EC89 compressor for a couple years now. As an Mechanical Engineer with a minor in Electrical, I observe that the motor assembly/capacitor is undersized for the mechanical energy it is asked to produce upon start up. The motor consistently struggles to get up to speed, requiring too much electrical current and then the breaker pops, and you're back to time zero. And the cycle repeats. In other words, the fundamental EC89 design stinks and it should not have been released onto the market in this way. I replaced the capacitor on mine with a more robust G.E. version and it has improved, but fundamentally, there are not enough motor windings to get the system going good & strong, each and every time. Shame on you, Hitachi.

Feb 08, 2011 | Hitachi EC89 4 Gallon Twin Stack Air...

1 Answer

My Hitachi twin stack air compressor is very hard to start and it frequently trips the reset switch when getting started first thing in the mornings. Even in warm weather i sometimes have to put a heater...

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 .

Feb 17, 2018 | Hitachi EC89 4 Gallon Twin Stack Air...

2 Answers

Trips thermal overload. power source ok. oil ok

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.

Oct 03, 2010 | Hitachi EC89 4 Gallon Twin Stack Air...

1 Answer

Keeps blowing the breaker... only 6 months old

This compressor is small however like other brands in this size range draw 13 - 15 amps. Thats quite a bit of power. The compressor has a thermal breaker that will begin to trip if compressor is hot. I am assuming that the breaker that is tripping is the one on the compessor. I have seen many hitachi breakers fail. Easy to replace with generic 20 amp, cost about $10. Before you replace anything, check amp draw with meter, if within specs try to determine what is causing heat.
cycling too many times per hour (check manual for recommended)
low power due to weak circuit or extension cord
using generator for powering compressor (not recommended)
using low quality oil (use synthetic if hot climate)
air leaking from intank checkvalve back to pump
If no reason to overheat then replace breaker on compressor to 20 amp but watch for overheating. Good luck

Jul 09, 2010 | Hitachi EC89 4 Gallon Twin Stack Air...

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