TM9-4120-400-14
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REFRIGERANT PRESSURE CHECK.
Testing
This task covers:
INITIAL SETUP
Refrigeration Unit Service Tool Kit
Goggles
Gloves
TESTING
1. Check that unit HIGH and LOW PRESSURE CHARGING VALVES are open and all four service manifold valves
are closed.
2. Both gages should read the same. Check the reading with the appropriate column in Table 5-2. If the system
is even partially charged, the pressure should be approximately equal to that shown in the table for the
appropriate ambient temperature. If the pressure is considerably less than as shown in the table, the system
does not contain enough refrigerant to continue the pressure check; proceed directly to leak testing. (See
3. Turn air conditioner on and operate in COOL mode with TEMPERATURE SELECTOR in full COOLER setting
for five minutes.
4. With unit operating allow gages to stabilize. Take readings of the two gages.
If discharge and suction pressures are at, or near, the same value a pressure equalizer solenoid valve L2
a.
If discharge pressure is low and suction pressure is normal, a low refrigerant charge is indicated.
b.
If discharge pressure is normal and suction pressure is either high or low, failure or maladjustment of the
c.
pressure regulator valve is indicated. (See table 5-3.)
If ice forms on evaporator coil, or evaporator coil does not cool, during operation, failure or malfunction of
d.
If discharge pressure is high and suction pressure is normal, a malfunction of quench the valve is
e.
indicated. If discharge pressure is above 540 psig, pressure relief valve malfunction is also indicated.
5. When pressure tests are completed, turn unit off and proceed with any maintenance action indicated.
NOTE
FOLLOW-ON MAINTENANCE:
5-49