What is the reasoning behind installing gauges? If the gauge does not read as expected, it's the fault of gauge? IMHO that is a dangerous fault in logic! If I was to look at the gauge in the garage now it would read 0, not because it's bad, but because there is no air in the system.
Only problem is the two air pressure gauges on the dash are not correct. They do not show full pressure, and the last time I started the coach one gauge reads 0 (yes, zero), and the low air alarm is sounding
My old trucks set for a day or 2, I expect to hear buzzer, see light and a gauge reading 0. That told me I had a slight leak in the system. If it would hold long enough to meet the law just hunt for it while looking for other problems.
Now the not reading full pressure is a issue that needs addressed before we move. Does the compressor cycle off, and the reading stay constant? Need to look at the governor, and little line to it. Might need cleaned, adjusted or replaced. If the compressor runs all the time, and you don't get full pressure, most likely you have a serious leak.