If a liquid line filter drier is clogged, what will appear in the sight glass?

When a liquid line filter drier becomes clogged, the refrigerant flow can be restricted, leading to an accumulation of liquid refrigerant on one side of the blockage. In this scenario, the sight glass will show bubbles. These bubbles occur due to the combination of liquid refrigerant at a lower pressure and the vapor that forms as the refrigerant struggles to flow past the obstruction.

The presence of bubbles indicates that the refrigerant is not flowing smoothly, and there is a phase change occurring, which further confirms the clogging of the filter drier. This visual cue helps technicians diagnose issues in the refrigeration system effectively, as they can identify potential blockages or malfunctions based on what they see in the sight glass. In a well-functioning system, you would expect to see a clear liquid and no bubbles, signifying proper flow and a clean filter drier.