Original poster: The site-glass is on the liquid line as it exits the compressor (outside). True, it has bubbles in it that never go away [Others her have told me to paint over it, as it has no diagnostic value..] This connection has gurgled ever since it was installed in 1988. I had it evacuated & recharged just as "PM", since it'd never been evacuated in 16 years. Outside unit is 1988 Carrier 3ton, and Carrier AH inside, also 3-ton (A/C-only). I didn't see the guages when the guy re-charged last year, so I didn't see what the charge was. Is there any way that the charge can still be improper, even tho the guages indicate and OK-charge? Any quick way I can tell if there's a metering device installed? I can post a pic of the lineset connection to the evap. Lastly, the gurgling is always present, no matter what the outdoor temp is, and no matter what the indoor temp is.
System is undercharged. Have the service company return to balance charge. Gurgling noise is refrigerant vapor as it enters metering device. The smooth, hissing noise you heard before was a full liquid head being presented to device - no vapor. When a system is underchaged, there is not enough volume to maintain head and the gurgling noise results. If there were a sight glass present in the liquid line, you would see the result of an undercharge as bubbles. There is a possibility that the system may have non-condensibles but need more info. Just curious - why did the system need an evac and recharge?