TM 9-4120-402-14
2-2. OPERATOR'S CONTROLS.
All necessary operator controls are illustrated in figures 2-1 and 2-2. Usage of controls is outlined in General Operating
2-3. INDICATORS
a. The TEMPERATURE PRESSURE FAULT indicator light (figure 2-1) comes on if the high pressure cutout, low
pressure cutout, coil frost, or thermostatic (heater cutout) switch opens. The switches are associated with the units
improper refrigerant charge.
b. The OVER CURRENT FAULT indicator light (figure 2-1) comes on if the motor controller is operating with too
high amp draw. This can be an indication of a component failure or wiring problem.
c. The OVER/UNDER VOLTAGE FAULT indicator light (figure 2-1) comes on if the motor controller is operating
outside its voltage range. This could indicate controller failure or a problem with input power.
d.
The HOT MOTOR CONTROLLER FAULT indicator light (figure 2-1) comes on if motor controller overheats.
CAUTION
Do not operate the air conditioner in the COOL mode if the refrigerant condition color indicator
has turned yellow or if numerous bubbles appear in the sight glass. Equipment damage can
result. COOL mode operation may be continued with the indicator color in the chartreuse band
or with only an occasional bubble appearing in the window, but the sight glass should be
rechecked after each four hours of operation to insure that the condition has not become worse.
e. The refrigerant sight glass (figure 2-2) 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 maximum cooling prior to
checking condition of refrigerant at 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 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 be charged. Either moisture or low charge indications
should be reported to supervisor.
2-4