TM 9-4120-402-14
5-18. REFRIGERATION SYSTEM TROUBLESHOOTING.
This task covers:
Examine
INITIAL SETUP
Equipment Condition
Unit operating in full COOL.
Examine.
(1) Check sight glass condition.
(a)
A bright green color indicates that the refrigerant is dry. As moisture content increases, the color
will gradually change to chartreuse and finally to pure yellow. A gradual change from green into
chartreuse over an extended period of time is normally an indication that the refrigerant
desiccant dehydrator is becoming saturated with moisture, if so, replace. A sudden change of
color is highly unlikely unless a rupture occurs allowing all refrigerant to escape.
NOTE
Be sure that the refrigeration system is under full load with the compressor running when
observing the sight glass for refrigerant condition.
(b)
The appearance of an occasional bubble in the sight glass can be expected, especially when
operating in a high ambient temperature. A gradual increase in the number and frequency of
bubbles is usually an indication that the refrigerant charge is being lost from the system through
a small leak. The number and frequency of bubbles will also increase if the refrigeration system
becomes overheated. The sudden appearance of numerous bubbles is usually an indication of a
(2)
Check for decreased cooling capacity. A reduction in cooling capacity will occur as a natural result if
refrigerant is lost from the system; with a total loss of cooling if all refrigerant is lost. However, in some
conditions a considerable proportion of the refrigerant may be lost before the reduced cooling capacity
is noticeable. Sudden or erratic reduction, or complete loss of cooling capacity is often caused by the
malfunction of one of the valves in the refrigeration system. Cooling capacity will also be reduced if
the refrigeration system becomes overheated. Check refrigerant system for leaks. (See paragraph 4-
15.)
(3)
Turn rotary MODE selector switch to OFF/RESET.
5-53