Fujitsu AS*A09LKC Service Instructions Manual page 28

Trouble shooting 4
INDOOR UNIT Error Method:
Room Temperature Thermistor Error
Detective Actuators:
Indoor Unit Controller PCB
Room Temperature Thermistor
Forecast of Cause :
1. Connector connection failure
Check Point 1 : Check connection of connector
Check if connector is removed.
Check if connector is erroneous connection.
Check if thermistor cable is open.
>> Upon correcting the removed connector or mis-wiring, reset the power.
OK
Check Point 2 : Remove connector and check thermistor resistance value
Thermistor characteristics (Approx. 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 (DC5.0V)
Make sure circuit diagram of indoor unit and check terminal voltage at thermistor (DC5.0V)
BLACK
1 1
BLACK
2 2
BLACK
3 3
BLACK
4 4
If the voltage does not appear, replace Controller PCB.
Indicate or Display:
Refer to error code table.
Detective details:
When Room Temperature Thermistor open or short-circuit is
detected at power ON.
2.Thermistor failure
0 5 10
33.6 25.9 20.2
40 45 50
5.30 4.35 3.59
THERMISTOR
( PIPE TEMP. )
THERMISTOR
( ROOM TEMP. )
02-06
3. Controller PCB failure
15 20 25
15.8 12.5 10.0
30 35
8.04 6.51