Fujitsu AU G18LVLB Series Service Instruction page 42

Trouble shooting 13
INDOOR UNIT Error Method:
Indoor Room Thermistor Error
Detective Actuators:
Indoor Unit Controller PCB Circuit
Indoor Temperature Thermistor
Forecast of Cause : 1. Connector failure connection
Check Point 1 : Check connection of Connector
Check if connector is loose or removed
Check erroneous connection
Check if thermistor cable is open
>>Reset Power when reinstalling due to removed connector or incorrect wiring.
OK
Check Point 2 : Remove connector and check Thermistor resistance value
Thermistor Characteristics(Rough value)
Temperature (°C )
Resistance value (k )
Temperature (°C )
Resistance value (k )
If Thermistor is either open or shorted, replace it and reset the power.
OK
Check Point 3 : Check Voltage of Controller PCB (DC 5.0V)
Make sure circuit diagram of each indoor unit and check terminal voltage at Thermistor (DC5.0V)
BLACK
1
CN32
BLACK
2
BLACK
1
CN8
BLACK
2
If the voltage does not appear, replace Controller PCB and execute the check operation again.
Indicate or Display:
Error code : 41
Detective details:
Indoor unit thermistor is open or short is detected always.
2. Thermistor failure 3. Controller PCB failure
0 5 10
33.6 25.9 20.2
40 45 50
5.3 4.35 3.59
H/E Thermistor
Room Temp. Thermistor
Outdoor unit : No indication
15 20 25
15.8 12.5 10.0 8.0
02-14
30 35
6.5