Fujitsu AB*30LBAG series Service Instruction page 51

Trouble shooting 4
INDOOR UNIT Error Method:
INDOOR UNIT
Indoor Heat Exchanger Temperature
Sensor Error
Detective Actuators:
Indoor Unit Controller PCB Circuit
Heat Exchanger Temperature Thermistor
Forecast of Cause :
1. Connector connection failure 2.Thermistor failure 3. Controller PCB failure
Check Point 1 : Check connection of Connector
Check if connector is removed.
Check erroneous connection.
Check if thermistor cable is open.
>>Upon correcting the removed connector or mis-wiring, reset the power.
OK OK
Check Point 2 : Remove connector and check Thermistor resistance value
Check Point 2 :
Thermistor Characteristics (Approx. value)
Temperature
Resistance Value (k )
Temperature
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)
THERMISTOR
(ROOM TEMP.)
THERMISTOR
(PIPE TEMP.)
If the voltage does not appear, replace Controller PCB.
Indicate or Display:
Indoor Unit
Outdoor Unit : No indication
Detective details:
When Heat Exchanger Temperature Thermistor open or short-circuit is
detected at power ON.
0°C 5°C 10°C
176 134 103
40°C 45°C 50°C
25.6 20.8 17.1
1 2
1 2 1 2
CN7 CN8
: Operation LED: 3 times blink, Timer LED: Blink,
Vertical swing LED: OFF / Blink
15°C 20°C 25°C
80.3 62.9 49.7
07-05
30°C 35°C
39.6 31.7