94734 only builds to 40 PSI?

by steve
(columbus,indiana,usa)

Central Pneumatic compressor tank label

Central Pneumatic compressor tank label

i have a dual tank protable air compressor that would build psi but would only get to about 40psi and stop,, but keeps running,


i have tried adjusting the pressures on the screws under the pressure switch , one is a metal screw the other is plastic,, which broke off and now cannot be adjusted ,,, i have tore the pressure switch apart ,, and now dont know where to get another or how it goes back together,, a parts manual , or where to get another pressure switch would be very helpful,, thanks,, steve

please send any info to:
fearlessheart60@yahoo.com
________________
Steve, your request for a manual is posted.

I believe your compressor problem is not (until you tried to adjust it that is) your pressure switch. :-)

When compressors run on yet the tank pressure only gets to a certain level and stops, that suggests to me a valve issue, a gasket issue, perhaps a check valve problem, or a piston seal failure.

Please see the Troubleshooting section on the sitemap page, about why compressors run and do not build pressure. Lots of things to check are noted there, along with some suggestions.

See, also, the pressure switch pages. You can probably substitute a non-OEM pressure switch for yours if you cannot find the exact same switch, with no negative effects. Just make sure the unloader valve is working when you change the switch.

Cheers,

Bill

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Dec 16, 2013
Air compressor problems
by: JIM

Hello; I am having the same problem with the compressor going up to about 50 psi and it wont go any higher to shut off. I did take the head off and everything looked good. I did notice with the air cleaner off it was blowing air out. I then took the air line off the head and it was pumping really well it would suck your fingers in. I then put the line back on and it blows air back out the air intake again. Then i took the air line going to the pressure switch and it was not blowing air out the intake again. It would seem that it is the pressure switch now. Its like when i hook everything back up it wont go past 40 psi and shut down, Would you have any ideas?
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Air coming out the intake port is symptomatic of valve failure. It is possible that the valve holds up to 40 PSI then lets go, and the pressure can go no higher in the tank after that.

I'm not sure what you mean by "It would seem that it is the pressure switch now.".

Bill

Jul 12, 2012
where to get parts (gaskets)
by: Anonymous

bill, Thanks a million, ive purchased an old craftsman belt drive compressor, that seems to do fine(for now lol) but since ive started tinkering with this central pnumatic,, and read the post and diagram on the gasket/reed issue,, i was wondering if and where did jason find the gaskets or material to fix the issue,, it seems like a real waste to just throw it in the junk pile because of a gasket,,, or now pressure switch that ive tore apart lol,,,
Thanks again for the feedback
Steve
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Steve,

See a local auto parts store for high-heat gasket material. One brand is Fel-Pro.

B.

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94734 low pressure and does not shut off at cut-out?

by C.J. Foster
(Metamora, IL)

Central Pneumatic 94734

Central Pneumatic 94734

Hi Bill,

I have a new Central Pneumatic Model #94734 compressor. It was actually purchased several years ago, but I just recently tried using it for the first time.

The first time I turned it on, it ran until the pressure reached 120 PSI (Owner's manual indicates factory cut-out is set at 115 PSI).

I hooked up a blow gun to it and there was a brief shot of air (less than a second) and then very low pressure. The guage stayed at 120 PSI.

I drained the air out of the tank and then I disconnected the air flow valve to see if there was a blockage at that point.

With the air flow valve still detached, I got the same results - pressure built in the tank but no air flow. I then put the air flow valve back on and with the air pressure at zero, I turned the compressor back on and this time it did not shut off at 120 PSI. I allowed it to build to 140 PSI and then I manually shut it off - doesn't appear the pressure switch is working now. I pulled the safety valve out and it did the same thing the air flow valve was doing - brief shot of air and then very low pressure. I also let the pressure guage go below 80 psi (factory set cut-in) and if I turn the compressor on, it runs.

I tried resetting the pressure adjustment screws (counter-clockwise to lower the cut-in and cut-out psi's), but had no success.

The compressor runs no matter what the PSI is at.

There seems to be several issues going on here. This is pretty disappointing considering the compressor is "brand new". I guess it would have paid to run the unit when I first received it to make sure it worked correctly then. I don't think I'll be able to return it 3 years later with no receipt:)

Any help is much appreciated!!!
___________________

CJ, you say "The first time I turned it on, it ran until the pressure reached 120 PSI (Owner's manual indicates factory cut-out is set at 115 PSI)." This is typical. El cheapo air gauges can be out by more than this, and the pressure switch may actually have shut the compressor off at the right setting, but the gauge was off.

Or it could be a variance in the setting of the cut out pressure in the pressure switch itself.

You say... "I hooked up a blow gun to it and there was a brief shot of air (less than a second) and then very low pressure. The guage stayed at 120 PSI." I am guessing you mean the tank gauge stayed at 120 PSI? What was the reading on the regulator gauge at this point, please?

"I drained the air out of the tank and then I disconnected the air flow valve to see if there was a blockage at that point." What do you mean by air flow valve, please? I don't know any part by this name.

Please comment here with responses to these questions, and then we'll press on.

Cheers,

Bill


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Nov 29, 2011
reply
by: C.J. Foster

Hi Bill,

If there was a way I could send you pictures, that might help me show you how my air output is configured. There is no guage at the air output before the air hose. I understand that is an option, but it did not come on this compressor. Nonetheless, the compressor is not responding to the cut-in and cut-out pressures, so I will assume the pressure switch is to blame for that problem.

The fact that when I open the air flow valve I am only getting a quick blast of air and then almost no air is still puzzling me. If you have access to this compressor's Operation Instructions or if you can inform me of a way to send you pictures, this may help me explain my setup. Regardless of whether there is a regulator valve or not, what could be causing the very low pressure at the air output even when the tank is at 120+ PSI?

Thanks!
C.J.

_____________________

CJ, start a new thread / topic on the ASK page, and you can upload up to 4 photos when you do that.


Nov 22, 2011
Further details
by: C.J. Foster

Hi Bill,

I don't have a regulater on this compressor. I have not altered it from the way it was when I bought it. It only has the pressure guage screwed directly into the tank. Basically all I was trying to say was the pressure guage reading was normal and was not fluctuating.

The air flow valve is a term I got out of the compressor's operating instructions manual. It is screwed into the air output and has a quick coupler on the end of it. It is basically a valve that you can turn the air flow on or off with at the point where you attach your hose to the compressor.

Since the compressor runs no matter what the tank's PSI is, I'm guessing the pressure switch is shot...even though it's brand new! I haven't checked on the cost of a new pressure switch yet, but considering this compressor was only around one hundred dollars brand new, I'm hesitant to invest much into it.

Hope this info helps to better explain my issues. Thanks again!

__________________

I have uploaded a photo of the air compressor to which I think you are referring. The photo shows a compressor with a pressure switch, tank gauge, and a regulator that controls the pressure of the air from the tank downstream to the air tool.

It would be very odd not to have a regulator on the outflow of the compressor.

If the compressor runs, and the tank pressure is not increasing, then it is not the pressure switch, but possibly a valve or gasket issue.

If the compressor runs and the pressure continues to increase, then I agree, it is probably the pressure switch that is failing.

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Air leaking from 95630 water drain valve?

by Sara
(Albany, NY)

Hello,

I have a central pneumatic compressor, model 95630. Turned it on the other day and realized no pressure was building up and air was leaking out of the bottom of the water drain valve. After unscrewing the valve I noticed the O-ring was broken. Can I just replace with any o-ring, or do I have to get a special ring/new valve?

Thanks!
_________________

Sara, that's an unusual issue.

If you can find an "O" ring that fits then I would say you would have no problem replacing the existing one with a new one. The application is benign regarding heat, and the fluids accumulating in the bottom of the tank are normally water and some compressor oil from time to time.

Maybe now is the time to pull the drain itself, put a 90 degree elbow in the drain port, run a short piece of poly air line tubing out to the side, and install a manual drain where it is visible and accessible?

Cheers,

Bill

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Builds up to 40 lbs and no more?

by robert
(pa.)

central pneumatic 2.5 hp/21gal. i let it run for a long time but it does,nt go above 40 lbs.when i shut it off i cant hear any leaks.
_____________________
Hi Robert. You are not alone with compressors that run and run and run, but don't build pressure.

One of the first things I check is whether or not the compressor is pulling in air. To do that, remove the intake filter, and feel around the intake port while the compressor is running. If a lot of air is pulsing back out the intake port, that indicates that the intake valve is failing.

Then, please look at the nav bar, click Compressor Issues, and then compressor troubleshooting. Read all the pages linked from "will not build pressure".

After doing the checks posted, if you still have problems, post here as a comment telling me what you have checked and what you have found, K?

Cheers,

Bill

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