SiUS331604E Troubleshooting by Error Code
Service Diagnosis 156
4.13 Thermistor Abnormality
Error Code C4, C5, C9, CA
Applicable
Models
C4, C5, C9: All indoor units
CA: FXMQ-PB models only
Method of Error
Detection
The error is determined by the temperature detected by the thermistor.
Error Decision
Conditions
The thermistor becomes disconnected or shorted while the unit is running.
Supposed
Causes
Defective thermistor
Defective indoor unit PCB
Disconnection of connector
Troubleshooting
Note: Error code and thermistor
Refer to page 231.
Caution
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Remove the thermistor from
the indoor unit PCB. Then,
insert the connector again.
Remove the thermistor from
the indoor unit PCB, and then
make resistance measurement
of the thermistor using a
multimeter.
CHECK 11
Normal (The error is caused by
defective contact.)
YES
NO
Replace the indoor unit main
PCB (A1P).
YES
Replace the thermistor.
NO
Is the thermistor
normal?
5 to 90 kΩ
Error Code Thermistor Except FXTQ FXTQ
C4
Heat exchanger liquid pipe thermistor
R2T R1T
C5
Heat exchanger gas pipe thermistor
R3T R2T
C9
Suction air thermistor
R1T —
CA
Discharge air thermistor R4T —
CHECK 11
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