Actually you can tell if the AC is running with low gas, you hear some hissing sound at the blower unit when it start up for the first 5 to 10 min, most running at 1/2 gas full it still create such sound. Syne AC will even have this sound if only 2/3 full.

With this knowledge I call up Panasonic just few days before warranty expired, they came and check, true enough the AC gas was not enough. It take longer time to cool the room and making hissing sound. He found the problem is at the join/fitting at three compressor, ask my own contractor came and redo the fitting and vacuum and refill gas. New got to Waite another 6 months.

Learn this from an experience AC installer many years back.

This also apply to car a/c compressor.

I am a person who like cold, and very sensative to a/c, bit of a/c problem i will feel it.