What does the presence of bubbles in a sight glass indicate about an R-410A system?

The presence of bubbles in a sight glass indicates that the system is low on refrigerant. When an R-410A system is properly charged, the sight glass should be clear or show a small amount of liquid without bubbles. Bubbles signify that there is not enough refrigerant circulating through the system to fully fill the evaporator coil, leading to a mixture of vapor and liquid. This lack of proper refrigerant can cause poor cooling performance and inefficiencies in the refrigeration cycle.

When a system is running low on refrigerant, it can struggle to absorb heat effectively, resulting in inadequate cooling. Therefore, observing bubbles in the sight glass is a clear indication that action should be taken, such as checking for leaks and recharging the system with the appropriate amount of refrigerant to restore its efficiency and functionality.