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 TM 55-1905-219-14-8
4-5. GENERAL (Continued).
Table 4-6. Air Conditioner Abnormal Operating
Pressures/Temperatures - Troubleshooting (Continued).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
3.
High suction pressure.
Step 1.
Overfeeding of thermal expansion valve.
Adjust expansion valve. Check installation of thermal bulb.
Step 2.
Leaky compressor suction valves.
Pump down, remove cylinder head, examine valve discs and valve seats.
Replace if necessary.
Step 3.
Capacity control system unloading at too high suction pressure.
Adjust capacity control valve to begin unloading at a lower control point.
Step 4.
Clogged bronze screen strainer in compressor suction manifold or temporary
suction felt filter not removed after initial operation.
Pump down, remove and clean screen strainer. Remove felt filter after 50 hours
of initial operation. If dirty, clean and replace for another 50 hours.
4.
Low suction pressure.
Step 1.
Insufficient refrigerant in system.
Add refrigerant.
Step 2.
Excessive superheat.
Adjust thermal expansion valve(s) to 80 - 10 superheat.
F
Step 3.
Restricted liquid line or compressor suction strainer.
Pump down, remove and clean strainer.
4-31
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