Why Does The Air Compressor Have Two Gauges?

Good question. Why does the air compressor have two gauges?

We are speaking, of course, about the little round displays that appear on most air compressors. These are shown in the image below, pointed out by the white triangles.

The faces of these gauges will show a range of pressure, usually from 0 PSI up to around 150 PSI. Don’t be alarmed if your pressure ranges are a bit different, as each gauge suits the compressor on which it is installed.

The pressure range displayed on your gauges might be 0 PSI to 100 PSI, or 0 to 250 PSI, or any other range, all depending on the pressure capabilities of that particular air compressor.

Air Compressor Help - Compressor Air Gauges
White triangles point to compressor air gauges

In the image of the two gauges, on this portable Porter Cable air compressor, the air gauge on the left is the one that is displaying the pressure setting on the air regulator, and the gauge on the right is displaying the pressure level inside the air tank.

Regulator Air Gauge

You will want to have a look at the page on this site about air regulators to better understand what they do. In short, the regulator is used to reduce the available tank pressure to the best operating pressure of the air tool or air using equipment.

As you turn the knob on the air regulator, the pressure display on the regulator air gauge will change too and indicate the pressure setting that the downstream air will receive.

Tank Air Gauge

Air Comrpessor Help - Air Compressor Air Gauges
Regulator air gauge and tank air gauge installed on a different air compressor

The tank air gauge displays the pressure that is inside the air tank. It is generally plumbed onto a nipple inserted into the tank so the air has an unimpeded flow to the gauge, although that’s not always the case. Regardless, air from the tank is exerting pressure inside the tank air gauge all the time and the face shows the actual pressure inside the tank.

If your air compressor has a cut in setting of 80 PSI for example, the tank air gauge needle will show a pressure drop as you use the compressed air from the tank, and when the tank gauge needle reaches the 80 PSI point, you should hear the air compressor start.

Immediately then, the needle on the tank air gauge will start to rotate indicating pressure is building in the tank. When the tank air gauge display reaches the cut out pressure, let’s use 110 PSI as an example, the gauge will show 110 PSI on the face, and your compressor should stop.

Tank Air Gauge Does Not Control Compressor Start & Stop

Neither the tank air gauge or the regulator air gauge have anything to do with starting and stopping your air compressor.

These two gauges display pressure readings. That is all.

It’s the compressor pressure switch that turns the air compressor on and off depending on the switch settings. It is the regulator that controls the pressure flow to your air tool.

If you have a question about your compressor air gauges, please feel free to ask it using the comment form below, and we’ll see if we can help.

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2 years ago

i have a husky c331h 33 gallon air compressor, what should my two gauges be set at?

3 years ago

My tank is a 29 GALLON w/ max 150psi. Last couple times I’ve used it the tank gauge stays at zero while filling up after I turned it on. I seem to get plenty of pressure and use my tools with normal performance. The release valve when pulled let’s out what seems like normal release pressure. Is this a bad gauge or is something else wrong. Two uses ago it filled up and the gauge seemed to go near 200 but as mentioned above is now at zero

Last edited 3 years ago by Steve
Ron Vachter
3 years ago

hi my air compressor tank gauge reads good, but the regulator gauge goes upto 50 psi. Why can’t i adjust it higher for the tools. my tank pressure is 200 psi. I rebuild the regualator, thank you for your help Ron.

4 years ago

I have my regulator set at 150 but when I activate my air chuck the regulated air gauge moves down? Solutions?

4 years ago

My comp nail gun says no more than a hundred psi what do I set the tank Gage to

Gene Ekenstam
4 years ago

On my 100 psi compressor, The manifold holding the gauges and pressure regulator broke and is no longer manufactured. Is there any problem if I construct one from regular brass plumbing fittings?

Derek meng
4 years ago

How is the compressor cooled?

4 years ago

Just got a little 2gal anvil air compressor. The tank gauge shows AN increase in psi, but the outlet gauge does not show any increase. There is no air traveling through the hose into the apparatus that is attached. Please help me! I just bought this air compressor, and am doing everything listed on the instructions to no avail!

4 years ago

I have porter cable 150 2.5 hotdogs, never been used. Fills up fine and reads 150 on left regulator. Right reads nothing and no air releases from new hose or adaptors. An suggestions
Thank you

Steve Belton
5 years ago
Reply to  Mike Stanton

Thank you for taking the time to answer my question everything you said makes perfect sense once again thank you Steve

Steve Belton
5 years ago

Do I plug my hose in the regulated air or the unregulated are both have a connection

Frederick C Blanchard
5 years ago

What gauge is telling me how much air is being provided to my tool? Tank or Reg.?
Thank you

5 years ago
Reply to  Mike Stanton

No I have never had it off and rarely use it. It’s about 20 years old so I thought I should buy a new regulator.

5 years ago

When I start my craftsman air compressor both the regulator gauge and tank guage both climb at the same level of pressure. Question 1. Is that normal? And when I turn the regulator knob either direction the regulator guage doesn’t move. Question 2. Is that normal/correct? Thanks. Mike

5 years ago

If a compressor output is gauge is reading 100psi and the pneumatic diverter is reading 30psi for its incoming pressure, what is the problem?

Alan Weaver
6 years ago

Can I use only a regulator gauge in my craftsman 5 HP compressor with the same pressure switch. My original dual gauge set up started leaking. Thanks for the help

Ian Williams
7 years ago

I have just bought a cobra 50 LTR compressor. Should I adjust the preset outlet pressure setting on the air tank or should this not be messed with?

I am spraying paint so only need 2 bar.

Thank you