Fujitsu ASU09RL2 Service Instructions Manual page 29

Trouble shooting 4
INDOOR UNIT Error Method:
INDOOR UNIT
Room temp. sensor 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 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 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) Check Point 3 :
Make sure circuit diagram of indoor unit and check terminal voltage at Thermistor (DC5.0V)
THERMISTOR
(PIPE)
BLACK
BLACK
BLACK
BLACK
THERMISTOR
(ROOM TEMP.)
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.
2.Thermistor failure
-10°C -5°C 0°C
(14°F) (23°F) (32°F)
55.46 42.36 32.67
30°C 35°C 40°C
(86°F) (95°F) (104°F)
8.051 6.52 5.316
1 1
2 2
CN4
3 3
4 4
3. Controller PCB failure
5°C 10°C 15°C
(41°F) (50°F) (59°F)
25.39 19.91 15.71
45°C
(113°F)
4.354
02-06
20°C 25°C
(68°F) (77°F)
12.5 10.0