Troubleshooting for SA Indoor Unit - FFQ, FCQ, FDBQ, FBQ, FHQ Series SiBE121021_C
326 Service Diagnosis
6.6 Thermistor or Related Abnormality
Remote
Controller
Display
The table below describes the 2 thermistor abnormalities.
Method of
Malfunction
Detection
Malfunction detection is carried out by the temperature detected by thermistor.
Malfunction
Decision
Conditions
When during compressor operation:
Thermistor input > 4.96 V
or
Thermistor output < 0.04 V.
Supposed
Causes
Disconnection of connector
Defective thermistor
Defective indoor unit PCB
Broken or disconnected wire
Checking
thermistors
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:
Refer to “Thermistor resistance check” on page 362 for detail.
Error Description
C4
Defective indoor heat exchanger thermistor system
C9
Defective room temperature thermistor system
Step Action
1 Disconnect the thermistor from the indoor unit PCB.
2 Read the temperature and the resistor value.
3
Check if the measured values correspond with the values in the table of thermistor
resistance check.
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