Moisture Indicators
Many sight glasses have a moisture-indicating chemical built into the sight chamber. The chemical will change color if there is moisture in the system. The chemical substance will turn pink if moisture is present in a system charged with either R-11, R-12, R-13, R-1J 3, or R-114. It stays blue if there is a safe minimum amount of moisture. With a system charged with R-22, R-500, or R-502, the chemical is green when dry, and pink when wet.
With some moisture indicators, the words "wet" and "dry" appear when the chemical changes color. Temperature is important. The higher the liquid temperature, the higher the moisture content needed to produce a color change. An indicator, if hot, can show "dry" even though the system has too much water. For accurate indicators, the liquid line should be as near 75SF (24°C) as possible.
It takes an hour to get a good reading. However, about eight hours are needed for the indicator to give an accurate color signal. Oil may turn the moisture indicator tan. Flushing the indicator with clear refrigerant will remove the color. However, if it continues to turn tan, the system has too much oil.
Alcohol placed in the system to absorb the moisture will affect the operation of the moisture indicator. Too much water or alcohol in the system will wash the chemicals off the indicator surface. Tire indicator will need replacing after the system is dried and the alcohol removed.
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Industrial