Central Pneumatic pressure in air line will not stay constant

by Travis
(Madisonville tennessee )

Central Pneumatic 99780 air compressor

Central Pneumatic 99780 air compressor

Hi, I have a central pneumatic air compressor 4hp 17 gallon Model 99780.


The tank will build pressure with no problem but when I start to use my air tools the pressure drops only after a few seconds of running.

I can hear the hose refill with air and it runs fin again for a few seconds.

It started this all of a sudden.

I've adjusted the regulator and have gotten it to return pressure back in the hose faster but it still will not hold pressure constantly.

Thanks for your help!

Comments for Central Pneumatic pressure in air line will not stay constant

Click here to add your own comments

Dec 31, 2015
3 gal pancake
by: Jeff

My regulator will not hold pressure. When I use a tool after a couple of shots with the brad nailer the regulator gauge drops 15 to 20 pounds.
Any answers?

Thanks!

Apr 19, 2015
On similar Model 99781 Air Regulator was the culprit.
by: Piddler

Model 99781 Air Regulator (built into the manifold)Impossible to find a rebuild kit for it. Harbor Freight customer service tried but could not ID my 6 year old unit. Solved by replacing existing manifold with Couplings and Tees with inexpensive regulator 'in-line' between tank gauge tee and the 'regulated flow' gauge tee. I relocated the pressure relief safety valve to the 1st tee which connects the incoming tank line and tank pressure gauge mounted on end. Had to cut a hole in cover housing. tee is end where Mounting was a little odd but it works fine.

Oct 17, 2014
Picture is up
by: Bill

Travis, I did get your new post, and have deleted them, and added the image here.

Please note that I've put a white circle around where I would tee off the line to see if I got good air pressure to my air tool, to help isolate the regulator to see if air passage through it was the problem.

As the compressor pumps air it flows down this white circled line into the tank. The gauge on the left displays the tank pressure.

With the compressor off, and the tank fully drained, you can put a tee into where the nut on the flex line attaches to the manifold. Add a coupler to the tee, and you now have an air supply to wherever you want it to go that is not affected by the regulator.

If you take the line completely off, and take it, along with a coupler that is the same as the one on your compressor now, you can acquire all the parts necessary to add the tee and coupler from a good plumbing shop. They will likely be brass and / or copper, and that's good.

Make sure you don't take the coupler that's installed on your compressor now, for if you do, you will have opened a path from the tank, through the regulator, to atmosphere, and all tank air will escape, however slowly it might, due to our perceived obstruction in the regulator body.

B.

Oct 17, 2014
Condensation
by: Travis

I apologize, I was referring to the other comment about the tank being filled with condensation. I had drained that out first.

I'll get some pictures up on a new thread of this ASAP.

I appreciate the help and very quick response!

Oct 17, 2014
Tank full - no air
by: Bill

While this... "Yes the tank has been emptied and the tank shows that it's full." puzzles me a bit, I'm expecting you meant that the gauge shows that the tank is full of air, after you drained it and ran it back up to cut out, yes?

OK, based on what you've written, I'm pretty sure that it is the regulator itself is the problem.

Rather than messing with the plumbing, replace the regulator and see what happens. Worst case, you'll have a spare regulator. Best case, your problem is gone.

B.

Oct 16, 2014
Pressure regulator
by: Travis

Yes the tank has been emptied and the tank shows that it's full. But when I run the grinder for example it loses power. But once I release the trigger you can hear the line refill

Oct 16, 2014
Compressor plumbing
by: Bill

I take it that you, for sure drained the tank?

As for the pressure switch, I cannot see where it is on your compressor as I cannot find an image of it.

Regardless, if the tank is empty when you disassemble the manifold, and you install your coupler upstream from the pressure switch, that will not affect the pressure switch "seeing" the pressure in the tank.

If you start a new thread, and add 4 images of your compressor, one from each side with the shroud off, and refer to your original post name, then I can add the images and we'll all have a better understanding of how to tee off to get air before the regulator so you can see if it is the regulator that is causing the problem.

Oct 16, 2014
Pressure regulator
by: Travis

Ok, once I take the cover off both the pressure regulator and tank pressure gauges are made into one bridge. Would I disconnect the entire bridge? If so will the pump still shut off at a certain pressure?

I hope this makes sense lol. That you!

Oct 16, 2014
Condensate?
by: Carls421

just to add to Bills suggestion, do you drain your tank of condensate? (Water) If the tank is full of water then the capacity of the tank is reduced considerably so you empty the tank of air quicker than the compressor can fill it again.
Carl

Oct 15, 2014
Air regulators fail
by: Bill

Among other things on your air compressor, air regulators fail.

If you are handy, tee off the discharge line upstream from the air regulator and feed your air tool with unregulated compressed air for a bit.

When you are using the air pulled before the regulator, are you experiencing the same issue with pressure drop.

If not, you need a new regulator I would expect.

Bill

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Central Pneumatic Air Compressor Issues.

Brand new 3 gal 100 psi oilless does not build pressure

by Imamoron4buyindisturd
(Cameron park ca)

Central Pneumatic pancake air compressor

Central Pneumatic pancake air compressor

Brand new 3 gal 100 psi .... Start up for the first time, all vales are positioned as directed but does not build any pressure so does not shut off. When I shut it off I hear air coming from under the gauges for about 10 seconds.

Comments for Brand new 3 gal 100 psi oilless does not build pressure

Click here to add your own comments

Aug 30, 2014
Will not build pressure
by: Bill

If it's brand new you did the break in run in... yes? Did you close the tank valve?

If you did, and the compressor runs but doesn't build pressure, it were me, given it's brand new, I'd take it back to the store and ask for a new one.

Or, if you wish to fiddle further, see the troubleshooting page on this site about why air compressors run but don't build air pressure for some tips.

If you have more info or question, please include the compressor model number, OK?

Bill

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Central Pneumatic Air Compressor Issues.

Central Pneumatic air flow problem

by Jerome
(Ocala,Florida)

central pneumatic 20gal compressor

central pneumatic 20gal compressor

I have this central pneumatic 20gal compressor and it doesn't properly power my tools. should I replace the pressure switch & regulator or just the regulator?

Comments for Central Pneumatic air flow problem

Click here to add your own comments

Sep 22, 2014
Air flow problem
by: Bill

Hey Jerome, is this a new problem or one you've had all along?

Reason I ask is if the compressor was supplying sufficient air to your air tools before and isn't now, then obviously something has changed on the compressor.

However, a small air compressor often cannot supply enough air for a high demand air tool.

Until we can figure out whether it's a new or old problem, no point in changing parts out yet.

Add a comment here with more details, please.

Bill

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Central Pneumatic Air Compressor Issues.

check valve

central pneumatic 3Hp pancake compressor--AC0306HPC/03941

central pneumatic 3Hp pancake compressor--AC0306HPC/03941

need check valve for central pneumatic 3Hp pancake compressor--AC0306HPC/03941---Colljim3@aol.com

Comments for check valve

Click here to add your own comments

Sep 29, 2014
Check Valve
by: Bill

Haven't found a schematic with the correct valve on it. Sorry.

Any check valve that fits the hole and has the same line connections will work. It doesn't have to be Central Pneumatic.

Here's one, for example.





Bill

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Central Pneumatic Air Compressor Issues.