20 Most Recent Hitachi EC25E 5.5 - Horsepower Air Compressor Questions & Answers

You need to spray the valve with WD-40 and let it soak a while. Then get on it with a pipe wrench. Home Depot has a new one. You will be able to replace it today. Try getting it out and put in a new one.
Plan B: Adjust the 'pressure switch' down to 140 PSI and maybe you can run that way for a while until you get a new pressure relief valve. Just turn the adjustment down a bit and keep trying it until it holds air.

(the pressure switch controls the air pressure by conttroling where the motor stops and starts)
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Unfortunately, you don't provide a Model number 'V73' is Version 7.3 of the Software running the control panel. They have model number like in the front page of this manual, and in this particular Manuals website you can use the search feature. https://www.manualslib.com/manual/1652200/Hitachi-Next-Series.html#manual ..

the regulator is used to control pressure. Is the knob turned completely clockwise. page 9 of instructions. Don't have yours copy and paste link https://www.metabo-hpt.com/docs/default-source/default-document-library/ec89_om.pdf?sfvrsn=51a32c66_0

I would check the main switch/speed control for a fault, assuming the battery is not exhausted that is.

notify a dealer or manufacturer

First, you have to determine how it is attached usually they are screwed or bolted into place or simply held into place by clips or pressure. But there are many different models so please post the model of your machine so it can be identified or even a photo.

This is a common problem with this model - the typical reason for this is overdriving the piston which is usually caused by air pressure being too high. It can also be from using it on thin or soft wood (using it to nail plywood to plywood etc)

This is not replacing an o-ring, unfortunately, this involves replacing the manifold #887-499 which contains the regulator. There are no regulator parts available.

check and test cut out may be faulty or failing

If u are talking about the bleed off that blows when the compressor shuts off. It should blow down for a short period then stop. If it dont stop your tank check valve is bad.

There is no battery on that air compressor.

So the first (most obvious but sometimes overlooked) thing - check to make sure the tank drains are closed. Listen for a leak at the pressure switch - it will continue to leak after the compressor shuts off. If this is the case then you need a check valve (Part # 53A on the breakdown) If it builds pressure but not enough to shut off and there are no leaks I would look at the valves located in the head (Part # 14 on the breakdown) - piston rings are not a normal failure part on this model but could also cause this.

This problem is usually caused by reed valves or blown gasket between head and valve plate. Easy to check. After the compressor reaches 45 to 50 psi, with compressor still running, remove the air filter and feel for good suction at the intake port. If the air seems to be blowing out of the intake, then valves are bad. If you feel good suction at the intake, then air is leaking from the discharge tubing or other fittings. Good luck

8 ounces of Synthetic Oil SAE15W40

Pressure gage A shows the pressure in the tank. Pressure gage B shows what you have adjusted the output pressure to be. If it is reading 0psi and it is new it is probably because the manufacturer has set it at that level. You have an adjustment valve on the front of your compressor. Rotate it until you see the pressure start to rise then keep going to where you want it set at.

Hitachi EC119SA 15 Amp 2 5 HP Lon Twin Stack Air Compressor Instruction...

here is a link to maintenance for these good luck Hitachi EC119SA 15 Amp 2 5 HP Lon Twin Stack Air Compressor Instruction...

Hitachi EC12 Portable Electric 2HP Oil Lubricated Air Compressor Parts Replace the entire regulator. You buy parts but you will be money ahead to buy a new one.

insure that there is no debris ie., free from filings from the nails used or or ceck the feeder ports where the nail enters before it lives the port ( check for damage orifice or abstractions to it

To remove the fan you will need a decent bearing puller - it is press-fit onto the armature shaft and doesn't come off easily.