TM 9-4120-403-14
(6) With one hand still on the suction return line, remove the sensing bulb from the container and warm it in the
other palm. If a temperature drop is not felt in the suction return line by the time the sensing bulb no longer feels cold to
the hand, the expansion valve is not opening and should be replaced. As soon as a temperature drop is felt, turn the air
conditioner to OFF.
(7) Slip the sensing bulb into its mounting loop clamps. Be sure the bulb is installed in its original position and
tighten the nuts and screws. Be sure the sensing bulb is making metal-to-metal contact with the suction line.
(8) Attach an accurate thermometer to an exposed surface of the suction return line adjacent to the sensing
bulb; use a small gob of thermal mastic to improve conductivity.
(9) Rewrap insulation on the suction return line, being sure to cover the sensing bulb.
(10) Start the air conditioner in the COOL mode with the thermostat set at fully DECREASE (counterclockwise)
and allow it to run about 30 minutes, then check to be sure the temperature in the suction line has stabilized and the
thermometer reading remains unchanged for at least 2 minutes.
(11) Note the pressure on the gage connected to the low pressure (suction) service valve. Find the saturation
temperature for the pressure gage reading (see table 5-1) and compare with the thermometer reading. The thermometer
temperature should be 10 +/-1 (5. 55 +/-. 5 0C) higher than the saturation temperature found on the chart.
F
(12) If the superheat setting is not within the limits shown above, replace the expansion valve.
Replacement
(2) Unwrap insulation from suction line so that sensing bulb is exposed. Loosen screws and nuts in clamps. Pull
bulb out of clamps.
(3) Disconnect flare nut on external equalizer line from expansion valve.
(4) Remove the two screws, flat washers, lockwashers, and spacers that attach the valve body to its mounting
bracket.
(5) Carefully remove the power assembly and cage assembly.
NOTE
If valve body flange is not damaged, do not remove (debraze) it from the system.
(6) If valve body flange is to be removed, purge the system with nitrogen and debraze the two tubes. (See para
5-42