Hitachi RAS-10HRNM, Service Manual, Page: 209 / 482

Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Insufficient cooling
process
Excessively high
discharge pressure
Insufficient air flow to the
outdoor unit heat
exchanger
Clogging of the outdoor unit heat
exchanger?
Remove the clogging
Obstacles at the inlet or the
outlet of the outdoor unit heat
exchanger
Remove the obstacles
Is the service area for the
outdoor unit sufficient?
Secure the service area
Correct fan speed? Replace the fan motor
Excessively high air
temp. to the outdoor unit
heat exchanger
Short-circuited air to the outdoor
unit?
Remove the cause of the short-
circuited air
Any other heat load near the
outdoor unit?
Remove the heat source
Excessively charged
refrigerant
Expansion valve opening Correctly charge the refrigerant
Non-condensate gas in
cycle
Check each temp. and each
pressure
Charge the refrigerant after the
vacuum pumping
Clogging of the
discharge piping
Check for clogging Remove the clogging
Failure or malfunction of
the expansion valve
Check for clogging Remove the clogging
Check the connection cord and
the connector
Replace the connector
Is there an operation sound from
the coil?
Replace the coil
Is the thermistor on the
compressor normal?
Replace the thermistor
Is the thermistor installed
correctly on the compressor?
Correctly install the thermistor
Malfunction or internal leakage of the 4-way valve
Check the temp. difference at the
inlet and the outlet of the 4-way
valve
Replace the 4-way valve
Excessively low suction
pressure
Malfunction or internal
leakage of the 4-way
valve
Check the Temp. Difference
between the Inlet and the Outlet
of 4-Way Valve
Replace the 4-way valve
Failure of solenoid valve
for bypass
Check refrigerant leakage of
solenoid valve
Replace solenoid valve
Discharge temp. of the indoor unit is unstable
Check the expansion valve of the
indoor unit in the same system
Replace the failed expansion
valve of the indoor unit
8 Troubleshooting
201
SMGB0060 rev. 1- 12/2010
8