Hitachi FSXN Series Service Manual page 172

8 Troubleshooting
Phenomenon
Excessively
High
Discharge
Pressure
Insufficient
Heating
Operation
Malfunction or Internal
Leakage of Reversing Valve
Malfunction of Check Valve
of Outdoor Unit
Excessively
High Suction
Pressure
Discharge Temp. of
Indoor Unit is Unstable.
166
SMGB0065 rev. 1 - 12/2010
Cause
Check for filter clogging.
Insufficient
Air Flow to Check for any obstacles
Indoor Unit at inlet or outlet of
Heat indoor unit.
Exchanger
Check indoor fan speed.
Excessively
High Air
Temp. to Check whether or not
Indoor Unit
short-circuited air exists.
Heat
Exchanger
Excessively
Check expansion valve
Charged
opening.
Refrigerant
Non-
Condensate Check refrigerant
Gas in Ref. quantity.
Cycle
Clogging of
Discharge Check for clogging.
Pr. Piping
Check temp. difference
between inlet and outlet
of reversing valve.
Check temp. difference
between inlet and outlet
of check valve.
Failure of
Bypass Check for leakage of
Solenoid solenoid valve.
Valve
Malfunction
or Internal Check temp. difference
Leakage of between inlet and outlet
Reversing of reversing valve.
Valve
Check for expansion
valve of indoor unit
in the same system.
Check Item
(Turn OFF Main Switch)
Remove clogging.
Remove obstacles.
Replace fan motor.
Remove cause of
short-circuited air.
Correctly charge
refrigerant.
Recharge refrigerant
after vacuum pumping.
Remove clogging.
Replace reversing valve.
Replace check valve.
Replace solenoid valve.
Replace reversing valve.
Replace failed
expansion valve of
indoor unit.
Action