Service Manual

Troubleshooting for FFQ Series SiUS181631EA
212 Troubleshooting
5.5 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 voltage between the both ends of the thermistor is 4.96 V and more or 0.04 V and less during
compressor operation.
Supposed
Causes

Disconnection of connector

Thermistor corresponding to the error code is defective.

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:
C4 : Indoor heat exchanger thermistor 1 (liquid pipe) (R2T)
C5 : Indoor heat exchanger thermistor 2 (R3T)
C9 : Room temperature thermistor (R1T)
Note: When replacing the defective thermistor(s), replace the thermistors as ASSY.
Refer to Thermistor Resistance/Temperature Characteristics table 1 on page 267.
Step Action
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.
YES
(R22250)
NO
Check the thermistor resistance
value.
YES
NO
Caution
Correct the connection.
Replace the defective
thermistor. (Replace the indoor
unit PCB (control PCB).)
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.