Hitachi EV-1.5N1, Service Manual

Page: 235 / 480

8. Troubleshooting
221
SMGB0079 rev.0 - 01/2013
8
Alarm code
21
Abnormality of High pressure sensor for RAS-(3-12)H(V)NP(E)
• The RUN LED flickers 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 O.U. PCB1?
Is 12V applied
between #1 and #3 of
the connector CN7
on O.U. PCB1?
Yes
Yes
Is voltage under
0.1V or over 4.9V
between #2 and #3 of
the connector CN7
on O.U. PCB1?
Abnormality of High
Pressure Sensor.
Connect correctly.
Faulty O.U. PCB1
Yes
No
No
No
Faulty O.U. PCB1
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