TM 9-4120-371-14
Problem with pressure regulating valve.
(3) Suction pressure too low.
Possible causes:
Dirty return air filter.
Discharge or return air louvers closed.
Partially blocked discharge or return air ducts or openings.
Dirty evaporator coil.
Cold return air.
Low refrigerant charge.
Fan motor not operating.
Problem with expansion valve operation.
Expansion valve superheat too high.
Plugged or kinked distributor tube.
Suction line or evaporator coil tubing restriction.
Moisture in refrigerant system.
(4) Suction pressure too high.
Possible causes:
High return air temperature.
Compressor not running.
Expansion valve bulb damage or poor contact with suction line.
Problem with liquid quench expansion valve.
Problem with regulating valve.
Problem with expansion valve.
5-20