TM 9-4120-404-14
d. The HOT MOTOR CONTROLLER fault indicator light (Figure 2-1) comes on if the motor controller overheats.
CAUTION
Do not operate the air conditioner in the COOL mode if the refrigerant color looks
yellow in the refrigerant sight glass or if numerous bubbles appear in the sight
glass. Equipment damage can result. COOL mode operation may be continued if
the refrigerant color is chartreuse or with only an occasional bubble appearing in
the window, but the sight glass should be rechecked every four hours of operation
to insure that the condition does not become worse.
e. The refrigerant sight glass (Figure 2-1) has a small chamber with a glass window through which the refrigerant
condition can be observed. It is installed in the liquid refrigerant line downstream from the condenser coil. 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 a maximum cooling prior to
checking the condition of the refrigerant in the sight glass. The sight glass is equipped with a center indicator that is
moisture sensitive. Dry refrigerant is indicated by green, it turns to chartreuse when the moisture content becomes
undesirable, and to yellow when the moisture 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 a milky appearance,
or frequent bubbles appear, the volume of refrigerant is low and the system should charged. Either moisture or low
charge indications should be reported to direct support maintenance for appropriate refrigerant system action.
2-3
