MXS Service Manual

SiUS121736EA Troubleshooting for RA Indoor Unit
Service Diagnosis 158
5.4 Thermistor or Related Abnormality
Error Code C4, C9
Method of Error
Detection
The temperatures detected by the thermistors determine thermistor errors.
Error Decision
Conditions
The voltage between the both ends of the thermistor is either 4.96 V or more, or 0.04 V or less with
the power on.
Supposed
Causes
 Disconnection of connector
 Thermistor corresponding to the error code is defective.
 Defective indoor unit PCB
Troubleshooting
Check No.01
Refer to P.209
C4 : Indoor heat exchanger thermistor
C9 : Room temperature thermistor
Note: When replacing the defective thermistor(s), replace the thermistors as ASSY.
YES
(R21870)
NO
Check No. 01
Check the thermistor resistance
value.
YES
NO
Caution
Correct the connection.
Replace the defective
thermistor.
Replace the indoor unit PCB
(control PCB).
Normal?
Normal?
Check the connection of
connectors.
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.