Hitachi RAS-(4-12)HNP(1)(E) - Abnormality of High Pressure Sensor for RAS-(3-12)H(V)NP(1)(E)

8 Troubleshooting
248
SMGB0087 rev.0 - 12/2013
Alarm code
21
Abnormality of High pressure sensor for RAS-(3-12)H(V)NP(1)(E)
• The RUN LED ickers and “ALARM” is displayed on the remote control switch.
• The unit number, the alarm code and the unit code are alternately displayed on the set temperature section.
The unit number and the alarm code are displayed on the display of the outdoor unit PCB.
- This alarm code is indicated when the pressure sensor output voltage decreases (less than 0.1V) or increases
(more than 4.9V) during the operation.
Is there connection problem of
CN7 on OU PCB1?
Connect correctly
Yes
No
Is 12V applied between number
1 and 3 of the connector CN7 on
OU PCB1?
Faulty OU PCB1
No
Yes
Abnormality of high
pressure sensor
Yes
Is voltage under 0.1V or over
4.9V between number 2 and 3 of
the connector CN7 on OU PCB1?
Faulty OU PCB1
No
Phenomenon Cause Check item
Action
(Turn OFF Main Switch)
Faulty top of compressor
thermistor
Fault Check resistance Replace thermistor if faulty
Incorrect connection Check wiring to PCB1 Repair wiring and connections
Faulty PCB1
Replace PCB1 and check
operation
Replace PCB1 if faulty
Indication of pressure value is
excessively high or low
Malfunction of pressure sensor
due to clogging wiring
Replace pressure sensor