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 TM 55-1905-220-14-8
4-5. GENERAL (Continued).
Table 4-11. Air Conditioner Cooling Coil Troubles Troubleshooting.
NOTE
Refer to paragraph 4-29 for air conditioning maintenance instructions.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
1. Loud hissing at thermal expansion valve.
Step 1. Insufficient refrigerant in system.
Add refrigerant as required.
Step 2. Clogged liquid line strainer.
Clean strainer screen.
2. Partial frosting of coil - failure to cool.
Step 1. Insufficient refrigerant in system.
Add refrigerant as required.
Step 2. Restriction in liquid line or clogged liquid line strainer screen.
Pump down and clean out line or strainer screen.
Step 3. Suction pressure regulator set too high.
Reset regulator to maintain refrigerant in coils at 20 less than compartment temperature
F
for bare pipe coils and 15 less for finned coils.
F
Step 4. Solenoid valve partially clogged.
Pump down and clean solenoid.
Step 5. Thermal expansion valve improperly set.
Reset expansion valve to 8- 10superheat.
3. No frosting of coil - failure to cool.
Step 1. Solenoid valve clogged.
Pump down and clean solenoid.
4-46
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