Mystery Air Loss - runs and puts no air into the tank and guages read "0"

by Dick Jenkinson
(Columbus Ohio)

Magnum dual cylinder (5 hp - HA!) 35 Gal Tank.Has run perfectly for 5 years.

Changed the oil yesterday now the air is disappearing.

I can't hear a leak.

Compressor runs and puts no air into the tank and guages read "0".

Did not run it long enough for pressure switch to trip but thermal circuit breaker did.

Adjusting the two limiter switches makes no difference. Problem probably in pressure switch (leaking ??) Any advice ??

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Bill says...

Dick, dump any air from the tank with the compressor off. Pull the line from the top of the pump that runs down into the tank,

Start the compressor.

Is air coming out of the pump? If there is air coming out of the pump, can you stop that air by putting a gloved finger over the outlet hole?

Post a response here, if you would.

Cheers,

Bill






Comments for
Mystery Air Loss - runs and puts no air into the tank and guages read "0"

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Feb 13, 2012
 Follow up pics to 2-10-12 post...
by: Anonymous

Bill, I finally had a chance to take side and top view photos of the manifold and solenoid. The tank is a horizontal style with the compressor and gauges on top. Do you think I need to replace the solenoid then? I notice there are tiny screws on the solenoid’s casing. Can the solenoid be ‘cleaned up’ internally to restore function or are are its innards too specialized to mess with?


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Clint, my, that is a venerable older control setup you have.

What I thought was a solenoid valve is, according to my research and the photos you uploaded, the pressure switch for your compressor. It's an older style Furnas switch, and is one they do not make any more.

The thing is, the pressure switch controls the on/off of your air compressor, but has nothing to do with the flow of air from the tank to the manifold.

As to the check valve, if there is none where the line from the pump head reaches the tank, then there must be one as part of the unloader valve assembly. Otherwise, every time your air compressor stopped, when it unloaded, all of the air in the tank would leak out, as the unloader valve stays open as long as the compressor is off.

Sure, pull the pressure switch apart and have a look. Can you fix it? I'm not sure that it's the problem, as I believe your compressor cycles on and off just fine, doesn't it?

The photo from the top shows a gauge at right, then the regulator in the middle, then a gauge at left.

If I understand correctly, you are getting no reading on either gauge... in other words, zero pressure indicated, right?

The gauge at right is connected directly to the manifold which is plumbed directly to the tank. Ergo, if the tank has pressure in it, and the gauge shows zero PSI, then that gauge is pooched.

The gauge at the left shows the pressure setting that you have made on the regulator center. It's this pressure setting that will be maintained as you use your air tools. If that gauge is showing zero PSI and the gauge at right is showing a PSI reading, then either the regulator is shut off or is itself blocking the air flow, or the gauge tot he left is pooched.

Cheers,

Bill
Feb 10, 2012
 Same issue, still unresolved. Check valve not apparent.
by: Clint in San Diego

Thank you for your site. I have a similar issue as this post with an 26-gallon electric Speedaire (model 5Z645C), I trouble-shooted using information here. I’m still stymied. I have strong air where air line meets tank, however I cannot find a check valve between compressor and tank. A portion of air line fitting on tank end branches off to what seems to be an electro-mechanical unloader valve switch…I un-stuck some parts under the manual pressure control knob between the gauges and was hopeful that might have been the issue. But alas, the gauges still get nothing. The entire guage assembly attached directly to tank. I don’t know if your forum accepts HTML, so here is a link to a pic I took, with identifying text added.

http://img706.imageshack.us/img706/2002/speedaireparts1.jpg



Uploaded with ImageShack.us

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Clint, it looks to me, looking at the photo, as though your air manifold has a solenoid valve on top of it. Does it? If so, that valve may be the shut off, and it may not be working. Thanks for the photo. The html seems to have worked. If you can, comment here again, with both photos, top and side view.

Bill
Dec 27, 2011
 SUCCESS !! WE HAVE AIR !!
by: Dick Jenkinson

Bill.....followed your direction and it was apparently the check valve. Was a little rusty (but is brass !) Cleaned up the spring,cap,and plastic/nylon "float" with oil and reinstalled.Ran all the way to top pressure and shut off. It even ran to the pressure its supposed to be. Hasn't in a couple years.

HATS OFF TO BILL. LISTEN TO HIM. HE KNOWS HIS STUFF !!!

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Very kind, I'm sure. Glad to have been of help.

B.
Dec 27, 2011
 check valve / unloader valve
by: dick

Sorry......Confused. The valve with the pin at one end of the line looks replacable. Just remove. Or is there another valve at the other end of that line that I should look at going directly into the tank ? Appreciate all your help !! I'm gettin' there.

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No problem. Go to the site map page, and read the pages under valves relating to check valves and unloader valves. All will be revealed. :-)
Dec 27, 2011
 Check valve.
by: Anonymous

Bill.......is that the small valve (1/2" X 1 1/2") with the pin that contacts the pressure switch cut off or another valve at the other end of the small tube that goes into the main tank supply ?

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That is the unloader valve, which, when the compressor shuts off, opens to bleed off air over the piston(s). When the compressor starts, the unloader closes, and air is fed into the tank. If the check valve is leaking, then the air that is supposed to be going into the tank bleeds out the unloader valve.
Dec 27, 2011
 Found the air !!
by: Anonymous

Bill......pulled the supply to the tank as you suggested. Strong and Steady flow under pressure.

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Then, if the air is coming out of the pump, it would travel down the line to the tank. The only thing stopping it from getting into the tank would be the check valve. I suspect then that your check valve may be leaking, and the air that is coming from the pump, rather than being directed though the check valve into the tank, is bleeding out to the unloader valve which is open while the air compressor is running.

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