Service Manual

Troubleshooting SiUS041638E
63 Service Diagnosis
4.5 Thermistor or Related Abnormality (Indoor Unit)
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
during compressor operation.
Supposed
Causes

Disconnection of connector

Defective thermistor(s)

Defective indoor unit PCB
Troubleshooting
Check No.01
Refer to P.92
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.