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 TM 5-4120-356-14
(a) Refer to figure 4-19 and remove the seal cap from the expansion valve.
Adjusting the expansion valve to increase refrigerant flow may cause a
floodback and damage the compressor. If refrigerant is fed too quickly, it will
not turn to gas in the evaporator. The evaporator will flood, causing a "sweat
back" or "frostback" down the suction line.
(b) Refer to figure 4-19 and locate the adjusting screw. Turning the adjusting screw counter-clockwise
increases flow and lowers both output temperature and superheat. Turning the adjusting screw clockwise
decreases flow and raises both output temperature and superheat. Four complete turns will raise or lower
superheat by approximately 2F (1.1C). Turn the adjusting screw to obtain superheat of 6.0F 1.5F
(-14.44C 0.8C).
(c) Allow the unit to run on "COOL" for approximately 20 minutes before adjusting to a new setting.
(d) Calculate superheat of expansion valve. If superheat is now 6.0 1.5F (-14.44 0.8C), no
further adjustment is necessary. If superheat is not correct, continue adjustment cycles until superheat
reaches the required temperature.
(e) Install the seal cap on the expansion valve and remove the thermometer bulb from the suction line
near the power bulb of the expansion valve (see figure 4-12).
(f) Reinstall the condenser fan (see paragraph 3-15b).
(4) Repair. If expansion valve is leaking refrigerant, repair valve in accordance with the procedures
given in figure 4-19.
(5) Replace If damage or defects are found which would impair serviceability, replace the expansion
valve. Refer to steps (6) and (7) for removal of defective valve and installation of a new valve.
(6) Removal.
(a) Turn the selector switch to the "OFF" position and disconnect the air conditioner from the electri-
cal power source.
(b) Refer to paragraph 3-15b and remove the condenser fan.
(c) Refer to figure 4-2 and release refrigerant from the system.
(d) Refer to figure 4-12 and 4-19 and remove the expansion valve.
(7) Installation.
(a) Refer to figure 4-12 and 4-19 and install the expansion valve.
(b) Perform any further maintenance of refrigerant components that maybe required at this time.
(c) Reinstall the condenser fan and a new dehydrator.
(d) Purge the refrigerant system in accordance with the procedures given in paragraph 4-8.
(e) Check the expansion valve and dehydrator for leaks in accordance with paragraph 4-4c. Repair any
leaks found in accordance with paragraph 4-4d.
4-44 Change 3
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