Troubleshooting for FFQ Series SiUS181631EA212 Troubleshooting5.5 Thermistor or Related AbnormalityError Code C4, C5, C9Method of ErrorDetectionThe temperatures detected by the thermistors determine thermistor errors.Error DecisionConditionsThe voltage between the both ends of the thermistor is 4.96 V and more or 0.04 V and less duringcompressor operation.SupposedCauses Disconnection of connector Thermistor corresponding to the error code is defective. Defective indoor unit PCBTroubleshooting If the cause of the problem is related to the thermistors, the thermistors should be checked prior tochanging 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 Action1 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 thermistorresistance check.YES(R22250)NOCheck the thermistor resistancevalue.YESNOCautionCorrect the connection.Replace the defectivethermistor. (Replace the indoorunit PCB (control PCB).)Replace the indoor unit PCB(control PCB).Normal?Normal?Check the connection ofconnectors.Be sure to turn off the power switch before connecting or disconnectingconnectors, or parts may be damaged.
