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TM5-4120-387-14
(3) If a leak is suspected or indicated, test per paragraph 5-9.
b.
Testing and superheat adjustment.
The expansion valve as supplied with the
unit is preset at the factory.
This valve should not be adjusted unnecessarily.
(1) Performs refrigerant pressure check on unit in accordance with
paragraph 5-12.
Leave gages or service manifold attached.
(2) Remove the suction line insulation from the area of the sensing bulb.
Observe location and position of bulb for reinstallation.
(3) Loosen the screws and nuts in the bulb straps that attach the sensing
bulb to the suction line, and pull the bulb out of the straps.
Use care to not damage or kink the capillary.
The following test must be conducted with the power on.
Exercise extreme caution.
Do not be misled by term “low voltage. ” Potentials as low as
50 volts may cause death under adverse conditions.
(4) Place the sensing bulb in a container of ice water or crushed ice so
that it is reduced to a temperature near 32°F (O°C).
(5) Set the Temperature control thermostat knob fully DECREASE (counter-
clockwise), fan speed to LO SPEED, place one hand on the exposed suction return
line, and start the air conditioner in COOL mode. If a drop in temperature is
felt on the suction return line, the expansion valve is not closing fully and
should be replaced.
If the return line temperature remains constant, check the
pressure gage; it should indicate approximately 58 ±2 psi (4.0 ±O.14 kg/cm2). If
the pressure is not within the above limits, test the operation of the quench
valve (para 5-20) and the pressure regulator valve (para 5–25) before attempting
adjustment of the evaporator expansion valve.
When performing the next test, turn the air conditioner to
OFF as soon as a definite drop in temperature is felt on the
suction return line.
If the test conditions are continued
more than a few seconds, the expansion valve will fully open
and an excessive flood-back of liquid refrigerant may damage
or destroy the compressor.
5-59
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