If you shut off the air compressor on full charge yet the gauge drops while the compressor is deactivated you definitely have an air leak.
Air compressor gauge leaking.
The compressor might even automatically restart just to counter the situation.
The valve on the outside of the pressure switch may look something like the one in the image.
Record the time it takes to load and unload the compressor.
You know the compressor is always leaking air as when you shut it down with a full charge of air in the tank after a short while you can see that the tank pressure gauge display is showing that the tank pressure is dropping.
To gauge the effect of an air compressor leak you can measure your plant s leak load.
What you need to do in this situation is pinpoint the source of the leak.
Unloader valve is leaking air.
It will load or unload based on the demand of.
When the air compressor reaches the normal cut out pressure and stops but you notice while the air compressor is off that air is leaking out of a valve attached to or perhaps inside of the air compressor pressure switch.
Compressor is constantly leaking.
In other words air leaks out of some part of the regulator all the time there is air in the tank.
Most regulators have a diaphragm inside.
It doesn t typically matter if the gauge is a 1 1 2 diameter face a 2 face diameter or a different size gauge face entirely yet buying the replacement gauge that is the same size as the one that you are replacing on your air compressor helps ensure that it will fit in the same space on that compressor.
If the air is leaking from the unloader valve then see the page under fixing compressor problems about air continuously leaking from the unloader valve for.
If your air compressor is leaking water it could be due to a bad drain.
If you shut down the compressor when the tank is filled with air and then find that the pressure gauge is showing a drop in pressure you know that the compressor is leaking air.
If air is leaking from the unloader valve when the air compressor is stopped that points to a problem with the compressor tank check valve not seating properly or its failure.
To do this operate the compressor in a load no load or start stop mode.
If you plug in the compressor the pressure switch response to the air leak and dropping compressor pressure will be to start the compressor again.