Air compressor keeps cycling and won't hold pressure when on!

I have a Hitachi EC12 Air compressor and it keeps cycling and won't hold pressure when its on... Any Ideas???

Unit can be found here

http://www.amazon.com/gp/product/customer-reviews/B0000225DO/ref=cm_cr_dp_all_top/104-3961875-1880720?ie=UTF8&n=228013&s=hi#customerReviews

 

you simply need to find where the leak is.

It could be anything from the pressure relief valve to the drain valve to a leak in the welded seam of the tank to a bad valve within the compressor that allows the air to pass backwards through the compressor.

If it leaks fast enough, you should be able to hear the leak and locate it.

 

I'm sorry I was not clear. It is not so much a leak as the pressure valve keeps releasing pressure. No matter how many PSI I have it set to the pump fills the tanks to full capacity (120psi) and then the pressure release valve kicks in for a bit dropping it down to say 80PSI. And on goes the pump to fill her back up! The unit hold pressure fine when it is turned off.

Hope that made more sense

 

yep, it does.

sounds like a defective pressure pop off or you are trying to pump up the pressure too much. At 120, I suspect that you may simply be trying to pump it up too high.


You need to set the pressure control switch to a lesser setting (if possible) so the pump does not reach that upper limit when running.

 

Thanks, I turned the pressure all the way down. Maybe the regulator is broken?? Could be why it keeps trying to hold a full tank at all times? I'm going to bring the compressor inside to take a better look tomorrow after work. I will post back then.

 

ok I got a chance to play around with it a little and this is what I have...

Even though the knob is set at 40PSI, when I turn the compressor on it keeps filling the tanks to full pressure (120PSI) . When I turn the compressor off it releases the air all the way down to 40PSI (where it was supposed to stop).

Also, when the tanks are at 120PSI I can't seem to get the regulator to adjust any higher then 40PSI now. If the tanks are at 120PSI and I turn the PSI knob up then the gauge should go up right?.Are all these problems symptoms of a bad Knob (pressure regulator?)

 

when you say pressure regulator are you speaking of a regulator on the outlet of the tank.? If so, that is not going to make a diff.
What I speak of is a pressure switch that controls when the pump is supposed to run.

explain what you are calling the pressure regulator so we can get onthe same page. I am not sure what is happening so I can't really give much more advice at the moment.

 

Sorry again.
I'm not sure of the part names.

When I say regulator .. I am talking about the knob you turn (clockwise or counter clockwise) to adjust the PSI. I assumed this was called a pressure regulator but am not sure.

 

Sounds like your having problems with a one way valve "Non return valve"
It prevents air from bleeding back into the pump or thru the valve that releases the head pressure so the pump can restart without back pressure.

Your regulator may be another problem.

This is a link to a manual. If it doesn't work search the net for "Hitachi EC12 Manual"

http://www.hitachi-koki.com/manual_view_export/pdf_manual_view.do?implementationWorkNumber=810&partsCode=C99078263&model=EC6B+%2F+EC6C+%2F+EC12+%2F+EC16&marketSeq=1

 

gwiz; did you notice he stated it holds air when off? Not a bad check valve if it holds air.

OK funky, I think you have a misunderstanding as to how this thing works.

there are two things we are dealing with that you are misunderstanding.

pressure control switch: makes the pump turn on and off when pressure in the tank reaches a preset lower and upper limit.

pressure regulator: a control used to regulate the pressure released into the hose. On your pump, this is adjustable and that is what you have been adjusting.

basically, when you turn the pump on, it should pump up (if pressure in tank is low) until it reaches the hight set point of the pressure switch and then shuts off.

As air is released from the tank, the pressure will drop. When it reaches the low set point of the pressure switch, the pump will be turned on and refill the tank.

That is that entire system.

The pressure regulator (the knob) allows you, as a user, to adjust the pressure released from the tank to whatever tool you are using.

From the link GWIZ provided, it seems your compressor has two pressure gages. The one on the tank will read the internal tank pressure and the other one is the pressure released into the hose.

From what I read, you should be able to crank the regulator up to full tank pressure or down to zero. Now when you have it high and then turn it down, you will have a release of pressure but that is only the regulator reducing the pressure in the hose (or if no hose attached, the small area of pipe after the regulator and some air from within the regulator) but should be a relatively small amount of air and should cease shortly after you have set the control.

the second gage reading should drop to whatever you set it to and the tank pressure gage should not change.


The more I read your posts, the more it sounds like you simply have a regulator problem.

 

Thanks Nap.. that made perfect sense. Do you think maybe the pressure regulator just isn't reading properly when it says its stuck at 40PSI.

 

"nap,
gwiz; did you notice he stated it holds air when off? Not a bad check valve if it holds air. "

Yes,
I'm not sure what he is saying. its not holding air.
In his post # 3
He states, it pumps up to 120 and goes down to 80 psi. turning the pump back ON
So its leaking when the pump is OFF.

He also stated it keeps cycling.
If its cycling to often then its leaking down when the pump is not ON.

 

Hey GWIZ.. Thanks for the replys..Just to be clear, the pump consistently loads and releases (through the pressure release valve) only when on. when it is off it does not release pressure. The cycling prob has been resolved.. The (on/off) pressure switch cover (if you look at the manual) was broke. The top clips in and the bottom screws in. The top clip broke off so it was not holding tight against some button causing it to cycle. I have repaired that and it is fine now. Though I Still have the problem with what we are guessing is the regulator ....

 

so it sounds like the pressure switch was not working and was allowing the tank to be overpressurized so the pop off would pop off, correct?

Anyway, so that is cured.

It is impossible to tell if the pressure is actually stoppng at 40 or not from here. I wouls suggest a test:

run the compressor. turn up the regulator to highet pressure (actual adjustment, not merely what the gage states) and then reduce the setting until yo see the regulated pressure start to drop. The run an air tool with that pressure. Then crank the pressure back up to max and run the tool again.

You should be able to notice if the pressure is higher the second time simply with how the air tool runs.

If it changes (indicating the pressure had actually increased) then it may simply be the gage. If it did not increase the pressure, the the regulator, most likely, is bad.

 

Thanks again NAP. I will try to run that test later on tonight after I'm done doing all my weekend errands and post back the results.

 

Hi rufunky,
Any update on this? My compressor is doing the exact same thing and I'm debating fixing it or buying a new one (not a hitachi, though). If it helps nap and gwiz, I can videotape what's going on with mine and upload it to youtube.

Mine actually fills the tanks, then the compressor stops, air escapes for about 10-20 seconds, then it sounds like the compressor tries to start up again, but it trips the circuit in my power strip.

Thanks for any help,
Steve.

 

I had the same problem with the EC12. The compressor would fully charge, but once the pump turned off, much of the air was released, as if the safety valve had triggered and failed to close.

The solution was actually very simple, and had nothing to do with the regulator, the pressure control switch or the safety valve. The non return valve (see number 53 on the exploded parts view posted by GWIZ on 7/21/07) was not sealing properly. This valve allows the pressure at the pump to be released when switched off so that the pump can be started again.

I took the valve apart and noticed that the rubber valve/stopper was binding on the edge of the cap that housed it. I figured that this was preventing the stopper from making contact with the valve seat. Using a sharp knife, I trimmed the top edge (closest to the spring) of the rubber stopper; just enough to allow it to move freely in and out of the cap (alternatively, one could also ream/sand out the interior of the cap).
Note: The non return valve on my EC12 had a cap on the top, instead of on the side as shown on the exploded parts view.
I reassembled the valve, and the problem was gone.

That’s it. It’s a very minor defect that can be fixed easily at no cost.

I hope this helps.

Paul

 

I called a Hitachi technician. My compressor was doing a little different. It fills up, then loses a little air then it restarts but sill start "spitting and belching" and then will "stall out".

The tech said to remove and clean the the non return valve. I have polio so I will have to get someone to help me remove this part. I do not know why I did not ask the tech how to clean the valve. Should I use some kind of solution to soak it in or just try to blow it out. Should i try to relubricate it when cleaned and if so, what type of lub should I use.

New to this forum,

JL

 

Thanks Paul worked like a charm.