TM 9-4120-402-14
5-20. REFRIGERANT SYSTEM PRESSURE CHECK.
This task covers:
Test
INITIAL SETUP
Tools
Equipment Condition
Refrigeration Unit Service Tool Kit
Goggles
Gloves
Test.
(1)
Check that all four service manifold valves are closed and unit DISCHARGE and SUCTION SERVICE
VALVES are open.
(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 shown in the table,
the system does not contain enough refrigerant to continue the pressure check; proceed directly to leak
(3)
Turn air conditioner on and operate in COOL mode with potentiometer TEMPERATURE control set at
maximum COOL position for five minutes.
(4)
With unit operating, allow gages to stabilize. Take readings of the two gages. (See table 5-3.)
(a)
If discharge and suction pressures are at, or near, the same value, a pressure equalizer solenoid
(b)
If discharge pressure is low and suction pressure is normal, a low refrigerant charge is indicated.
(c)
If discharge pressure is normal and suction pressure is either high or low, failure or
maladjustment of the expansion valve is indicated.
(d)
If ice forms on evaporator coil, or evaporator coil does not cool during operation, failure or
malfunction of evaporator expansion valve is indicated.
(e)
If discharge pressure is high and suction pressure is normal, refrigerant overcharge is indicated.
(5)
When pressure tests are completed, turn unit off and proceed with any maintenance action indicated.
(6)
Turn rotary MODE selector switch to OFF/RESET.
NOTE
FOLLOW-ON MAINTENANCE:
5-55