TM 9-4120-405-13&P
Air Conditioner. Refrigerant sight glass (15) is the only visual indicator used on the air conditioner. The sight glass is a
port through which the refrigerant condition can be seen. 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 the 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 an opaque, milky appearance, or frequent bubbles appear, the volume of refrigerant is low and the system
should be charged. Refer to TM 5-4120-384-14 for maintenance.
CAUTION
Do not operate the air conditioner in the COOL mode if the refrigerant color has
reached the yellow bank 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 window, but the sight glass
should be rechecked after each 4 hours of operation to ensure that the condition
has not become worse.
Section II. OPERATOR PREVENTIVE MAINTENANCE CHECKS AND SERVICES (PMCS)
2-4. GENERAL. Preventive Maintenance Checks and Services (PMCS) are essential to the efficient operation of the
trailer-mounted, generator-set powered, air conditioner and to prevent possible damage that might occur through neglect
or failure to observe warning symptoms in a timely manner. Checks and services performed by operators are limited to
those functions which are described in table 2-1.
a. Before You Operate. Always keep in mind and observe the Warnings and Cautions. Perform your before (B)
PMCS.
b. While You Operate. Always keep in mind and observe the Warnings and Cautions. Perform your during (D)
PMCS.
c. After You Operate. Be sure to perform your after (A) PMCS.
d. If Your Equipment Fails to Operate. Troubleshoot with proper equipment. Report any deficiencies using DA
Form 2404. See DA PAM 738-750 for instructions.
e. Perform weekly, as well as before operations, PMCS if:
(1) You are the assigned operator and have not operated the item since the last weekly.
(2) You are operating the item for the first time.
NOTE
If the equipment must be kept in continuous operation, check and service only
those items that can be checked and serviced without disturbing operation. Make
the complete checks and services when the equipment can be shut down.
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