How to replace an air gauge, you say? Well the nature of the compressor air gauge that likely comes along with a low-cost DIY type air compressor, and they are just that…low cost. Both the compressor and the air gauge… cheap!
This means that the gauges are not built to handle heavy, prolonged use which might break a gauge needle, and they will fail due to internal corrosion or mechanical fatigue. That might take months or years, depending on the use and the condition of the compressed air the gauge is monitoring.
Further, for many of us, our air compressors are relegated to the basement or workshop where things pile on them, other things run into them, and ultimately the gauge face gets cracked or the entire gauge might get broken off.
Time to replace your air gauge? It is pretty easy. Here is how.
There Are Two
First, know that most DIY type air compressors come with two gauges. One of the gauges is to give you a reading of the air pressure in the compressor air tank.
The other gauge is normally found as part of the regulator assembly on the discharge line from the tank to the outlet coupling. This gauge is to show you the pressure setting on the regulator, and shows the air pressure for your downstream application.
Air Gauge Configurations
As depicted in the photo the air gauge has a face on which the pressure range for that gauge is visible. That scale is protected by a carbonate or glass face, which is susceptible to breakage.
The diameter of the standard air gauge face is 1 1/2”. Another air gauge standard diameter is 2”. Yours is likely one or the other, and I would lean to the 1 1/2″ size as being typical, as it costs the manufacturer less money to install a smaller gauge on an air compressor.
The gauge will be equipped with a male thread fitting on the bottom or the center of the back. It does not matter to the gauge whether it is turned into the air line from a male thread on the bottom of the gauge, or a back located male thread.
The different locations of the mounting threads are purely for the convenience of the installer or the location of the air line into which the gauge is threaded.
You can also purchase air gauges that are panel mounted to facilitate an industrial type installation. A panel mount gauge typically has a back mount, and comes with a space ring that allows the gauge to fit into a through hole on the panel, without dropping completely through. An installer may have to run an air line to the back of the panel mounted air gauge.
Air Gauge Pressure Ranges
The typical DIY type compressor air gauge will have a pressure range of 0-160, maybe 0 to180 or even 0-200 PSI.
As long as the air gauge you obtain as a replacement shows the normal cut in pressure level of your compressor, and the normal cut out pressure level, that it is a 180 PSI versus a 200 PSI really makes no difference.
Specialty application gauges will have different pressure scales on them, depending on the application for that gauge.
How To Buy Compressor Gauges
If your old gauge is in good shape (or even if it is not) take it with you to the shop so that you can match-the-hatch and get the same size fitting, same sized face, and same pressure range.
If your new gauge is a back mount type, and your existing gauge has the fitting on the bottom, the new gauge may not fit. It is always good to get the same size and style if at all possible.
If your air gauge is totally gone, opt for a 1 1/2” face, 0-200 PSI pressure range, with a 1/4” male NPT fitting on the bottom. That is a pretty good fit for many DIY type air compressors.
How Much Are Compressor Gauges?
The new gauge will set you back somewhere between $5-$15 or so, depending on where you buy it.
If the gauge is priced more than that, it is possible you are buying:
- a) an overpriced air gauge
- b) a much better quality air gauge than needed
- c) a specialty gauge of some sort
- d) a different compressed air component entirely 🙂
Doing The deed
Make sure you unplug your compressor and open the drain valve in the tank to empty the air pressure completely. Else, when your air gauge gets down to the last thread, one final turn will shoot that sucker right up and out of your hands, as the air pressure in your tank blasts to atmosphere. Be careful!
Some gauges have wrench flats to use a wrench, some rely on you turning the body of the gauge to unscrew the thread. If the gauge is not broken before you do this, it quite likely will be after you do so!
Anyway, unscrew the old gauge after you double check that there is no air in the compressor tank.
Use pipe dope or teflon tape (better the former than the latter as far as I am concerned) to coat the threads on the new gauge.
Turn the new gauge into the compressor boss until snugly-hand tight, and then turn if just further enough to orient the air gauge face to where you can best see it.
No need to over-tighten, as the pipe dope will seal the threads if they are screwed in just past hand tight and if you tighten too much, the gauge may break.
Plug in your compressor (after you have closed the tank drain valve) and away you go. You might want to put some soapy water around where the gauge threads go into the compressor just to satisfy you that the gauge fitting is not leaking.