Indicators - TM-5-4120-393-140028

TM 5-4120-393-14

OPERATOR'S CONTROLS REAR

2-3. Indicators. The refrigerant sight glass is the only visual indicator used. Liquid refrigerant actually flows through the

sight glass chamber only during cooling cycles when the air conditioner is in operation in the COOL mode. The unit must

be operated approximately 15 minutes at maximum cooling with an ambient temperature higher than 70F (21C) prior to

checking the condition of the refrigerant at the sight glass. The sight glass is equipped with a center indicator that is

moisture sensitive. Dry refrigerant is indicated by green, it turns chartreuse when the moisture content becomes

undesirable, and yellow when the level becomes unacceptable. Excessive moisture in the refrigerant may damage or

possibly destroy the compressor. If the liquid refrigerant observed in the sight glass has an opaque, milky appearance, or

frequent bubbles appear, the volume of refrigerant is low and the system should be charged. Either moisture or low

charge indications should be reported to direct support maintenance.

CAUTION

Do not operate the air conditioner in the COOL mode if refrigerant color has

reached the yellow band or if numerous bubbles appear in the sight glass. COOL

mode operation may be continued with the refrigerant color in the chartreuse band

or with only an occasional bubble appearing in the sight glass, but the sight glass

should be checked every four hours to insure that the condition has not become

worse.

2-2