Fujitsu AS*A09LKC Service Instructions Manual page 29

Trouble shooting 5
INDOOR UNIT Error Method:
Indoor Heat Exchanger Temperature
Thermistor (Middle) Error
Detective Actuators:
Indoor Unit Controller PCB
Heat Exchanger Temperature Thermistor (Middle)
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 Heat Exchanger Temperature Thermistor (Middle) open or
short-circuit is detected at power ON.
2.Thermistor failure
0 5 10
176 134 103
40 45 50
25.6 20.8 17.1
THERMISTOR
( PIPE TEMP. )
THERMISTOR
( ROOM TEMP. )
02-07
3. Controller PCB failure
15 20 25
80.3 62.9 49.7
30 35
39.6 31.7