Service Manual

SiUS121827E Troubleshooting for SA Indoor Unit
Part 6 Service Diagnosis 187
Note
Reference
6.6 Thermistor or Related Abnormality
Error Code C4, C5, C9
Method of Error
Detection
The temperatures detected by the thermistors determine thermistor errors.
Error Decision
Conditions
The thermistor is disconnected or shorted while the unit is running.
Supposed
Causes
 Disconnection of connector
 Defective thermistor(s)
 Breaking of wires
 Defective indoor unit PCB
Troubleshooting If the cause of the problem is related to the thermistors, the thermistors should be checked prior to
changing the indoor unit PCB.
To check the thermistors, proceed as follows:
1. Disconnect the thermistor from the indoor unit PCB.
2. Read the temperature and the resistance value.
3. Check if the measured values correspond with the values in the table of thermistor resistance
check.
C4: Indoor heat exchanger thermistor 1 (liquid pipe) (R2T)
C5: Indoor heat exchanger thermistor 2 (R3T)
C9: Room temperature thermistor (R1T)
When replacing the defective thermistor(s), replace the thermistor as ASSY.
Check No.01 Refer to P.232
YES
(R24056)
NO
Check No. 01
Check the thermistor resistance
value.
YES
NO
Caution
Correct the connection.
Replace the defective
thermistor(s).
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.