About Air Compressor Gauges

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While not essential for using your air compressor, it’s always useful to know a bit about air compressor gauges.

The vast majority of DIY, workshop and small plant air compressors will have two air gauges.

One of them displays the compressed air pressure that is the tank at that time. If you can see how the air gauge is mounted, the tank air gauge is always plumbed directly to the tank.

It is the tank air pressure gauge, a typical one of which is shown below,  that fluctuates all the time as air is being pumped into the tank by the compressor pump, and as compressed air is being used. The tank air gauge can be back mounted as is the one in the image below, or it can have a mounting nipple on the bottom. Both styles are relatively inexpensive at $6-$10 or so, both styles have pressure ranges from 0-160 PSI or perhaps zero to 200 PSI depending on the brand, and the choice between the two mounting styles is made based on how the gauge is attached to the compressor.

Tank air gauge for compressor

If your current tank air gauge has a pressure range of 0-160 PSI for example, and you need to replace it, feel free to replace it with one that has a pressure range of 0-200 PSI should that be the only gauge available. These are dumb devices, and as long as the pressure range of the gauge you select is equal to or greater than the upper pressure range of your compressor pump, you are good to go.

The thing about air compressor gauges is that eventually tey do rust out. They do break. If that happens, replace the gauge immediately as you do want to know what’s happening, air pressure wise, inside the tank.

It is the tank air gauge that displays the air compressor cut in and cut out pressures, and will tell you very quickly, if you know what these pressure settings are when the pressure switch is operating properly, if the switch settings are changing. This indicates a problem with your pressure switch.

Regulator Air Gauge

The other air gauge on a typical air compressor is the one that is plumbed to the air compressor regulator.

This is an important gauge as it displays the pressure setting of the regulator. Your tank gauge may show 150 PSI when the tank is full, yet the pressure gauge may display only 80 PSI, or whatever the pressure setting is on that air regulator.

compressed air regulator gauge

On your air compressor, your air regulator gauge may be plumbed directly onto the air regulator, as is the one in the image above, or it may be installed in a panel with the air line to the regulator plumbed from behind.

By turning the air regulator knob in one direction you increase the pressure setting and in the other, decrease it. Regardless of what way you turn the regulator knob, the air pressure regulator gauge will display that setting.

There is one time it will not, however. A regulator can only regulate pressure that is higher than the setting. If, for example, you turn the knob to increase the downstream pressure, and say for example your tank has 100 PSI in it, as you turn the knob on the regulator to increase the pressure setting, you will see the gauge needle indicate a higher pressure setting, but only until the regulator setting reaches 100 PSI – the pressure in the tank. Even if you continue turning the regulator knob to dial up a higher pressure, the display on the gauge will only go as high as the pressure that is available in the tank.

If you want your regulator gauge to register a higher pressure than 100 PSI, then you have to have more than 100 PSI in the tank.

About Air Compressor Gauges

Both the tank air pressure gauge and the regulator gauge can be the same size (typically 1 1/2″ in face diameter) and with the same mounting thread (typically 1/8″ NPT) regardless if the mounting is bottom or back. They can also display the same or different pressure ranges depending on the ranges you want available.

In the smaller, DIY type, air compressors, you frequently see the tank gauge being 1 1/2″ in diameter and a 1″ diameter regulator gauge.

Again, regardless of the size, both air compressor gauges display the pressure that is flowing through the mounting hole to the sensor inside, and as long as a new pressure gauge that you may acquire fits the mount, fits for the diameter, and has the same pressure range as the original, feel free to use any gauge you can acquire.

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Chris Queen
Chris Queen
October 22, 2019 3:46 pm

I have a Central Pneumatic 6 gal. 1.5 hp oilless portable air compressor. Item number 67696. The tank pressure gauge is leaking inside the gauge. Where can I get a replacement gauge that will fit? The back of the gauge measures 1.5 inches, the face measures just a little over 1.5 inches.

steve
steve
Reply to  Chris Queen
March 5, 2021 2:17 pm

I’m looking for the same gauge…let me know if you find out where to get one. Thanks

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  steve
March 5, 2021 3:51 pm

Steve, did you read the whole thread? I thought there was some decent advice there.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Chris Queen
October 22, 2019 3:49 pm

Chris, your post was moved to this page about compressor gauges.

You are on the right track when you measured the face. Now, look at the gauge face and see the pressure range. Is it 0-150 PSI, or different? Regardless, determine what the range is of the gauge you have, and get one that has a range as close to this. Likely your gauge is standard, meaning there will be lots.

Last, does the mounting thread come out of the bottom, or the back of the gauge?

Once you have determined this, Google replacement air gauges, and pick one that has the same specs as outlined above. There are lots, and you should have no problem at all finding one that will do the job for you.

Chris Queen
Chris Queen
Reply to  Fix My Compressor Moderator
October 22, 2019 4:47 pm

Hi Willyr, Thank you for the rapid response. The gauge reads to 270 psi. It is a top mount which I have not found nothing with a top mount. I have searched Google, Amazon and Ebay. Do you know of any places online where I could order such or that offers such as I can not drive due to a stroke.

Best Regards,
Chris Q.

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Chris Queen
October 22, 2019 5:52 pm

Chris, what kind of compressor is yours? I don’t know of any general purpose compressors that can pump up to 270 PSI. What is the cut in and cut out pressure of the compressor?

Chris Queen
Chris Queen
Reply to  Fix My Compressor Moderator
October 22, 2019 7:02 pm

The cut in is 120 and cut out is 150. I have no idea why the tank gauge reads up to 270 but that is just what is on the face of the tank gauge. Here is a photo of the compressor.It is a central pneumatic.

Central Pneumatic.png
Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Chris Queen
October 22, 2019 7:20 pm

Replace that one with one that runs 0-170 PSI or so. Lots of those. Given that the gauge goes into the manifold, you may have to extend the gauge port by adding a nipple and then using a bottom mount gauge. Upside down, I know, but who cares, really? The gauge should cost about $10 and many are available on line.

I suspect that Harbor Freight may just tell their Asian suppliers to use the same gauge on all compressors, regardless of the actual pressures involved.

This is not an expensive compressor, and as such, measure rebuild and fixing costs against the cost of a new cheap compressor. It may be best in the long wrong to replace the whole unit.

Chris Queen
Chris Queen
Reply to  Fix My Compressor Moderator
October 22, 2019 8:25 pm

I appreciate the info Willyr. I did not think about just getting a bottom mount and placing it on upside down. I don’t care at all really as long as the thing holds air and cuts off when it should I am happy lol.

Best Regards,
Chris Q.

John Billigmeier
John Billigmeier
May 11, 2016 2:00 pm

When replacing gauges and switches, do you use tape or any type of sealant on the threaded surfaces? How tightly do you install threaded fittings?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  John Billigmeier
May 14, 2016 10:12 am

As long as you are careful with winding the tape on the thread against the grain, so that the tape tightens as you thread in the fitting, use the tape. If you overlap an air path, it will obstruct it, which is why we say apply it carefully. Liquid or paste pipe dope is preferable, but we, too, have used tape. Turn the gauge until it’s feeling tight, and then use a wrench on the gauge flats above the thread to finally turn the gauge so that it is oriented in the direction you want. That should do it.

Jamie Chown
Jamie Chown
April 11, 2016 8:42 am

Not sure of the model but its a 20 gallon 1.5 HP direct drive oil free upright compressor.
It has from day one always had a small leak but since i rarely used it i never addressed it when i should have (especially under warranty!). Now it is leaking real badly all around the tank pressure gauge. When i say around i mean from the gauge itself, not the fitting where it plugs in. I bought a new replacement from Lowes, installed it and it leaked the same place but worse (faster). I doubt at this point i have a faulty gauge? I thought the gauges were air tight, how could two of them leak – is it bad luck or indicative of a different issue?

Fix My Compressor Moderator
Fix My Compressor Moderator
Reply to  Jamie Chown
April 15, 2016 8:51 pm

A bit hard to respond as we don’t know where on the gauge the air is leaking from. When you say all around the gauge, where exactly? Where the nipple threads into the manifold or around the face. If it is leaking around the threads, consider that the casting or thread boss itself may be cracked. Please provide more info. We looked at the image but it did not indicate the location of the leak.

Jason Strong
Jason Strong
January 20, 2016 3:40 pm

My dad was given a air compressor by a friend and he has no idea how to use it. He is trying to figure it out on his own, but he hasn’t gotten to far with it yet. This article has some great points on the gauges that I think can help him at least get started.

Douglas Brown
Douglas Brown
October 9, 2015 3:17 pm

Keeping air compression gauges in tip top shape is extremely important in order to avoid any dangerous situations or accidents. We will probably be making our own, and we want all the tips that we can get. Thanks for all the tips and information regarding pressure gauges and things like it.