Hitachi FS3 Series, Service Manual

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40
TROUBLESHOOTING
Alarm Code
21
Abnormality of High Pressure Sensor for Outdoor Unit
n
”RUN” light flickers and ”ALARM” is indicated on the remote control switch.
n
The unit No., alarm code and the unit code is alternately indicated on the set temperature section, and the
unit No. and alarm code are indicated on the display of the outdoor unit PCB.
‘
This alarm code is indicated when the pressure sensor voltage decreases lower than 0.1 V or increases
higher than 4.9V during running.
Is the connection
CN7 of the outdoor unit
PCB1 bad?
Yes
Connect correctly.
No
Is 12 VDC applied across
#1 and #3 of the connector
CN7 of the outdoor unit
PCB1?
No
PCB1 defective.
Yes
Is voltage under 0.1 VDC
or over 4.9 VDC across #2
and #3 of the connector
CN7 of the outdoor unit
PCB1?
No
Faulty PCB1
Yes
Yes
Clogged Check Joint? Replace check joint.
No
Abnormality of High
Pressure Sensor.
.
Phenomenon Cause Check Item
Action
(Turn OFF main switch)
Fault
Check output voltage is
correct.
Replace pressure sensor if
faulty.
Faulty High
Pressure
Sensor
Incorrect Connection Check connections.
Repair wiring and
connections.
Faulty PCB
Replace PCB and check
operation.
Replace PCB if faulty.
Indicated
Pressure Value is
Excessively High
or Low
Malfunction of Pressure
Sensor due to Faulty Check
Joint
Check for clogging of
check joint.
Replace check joint.