Fujitsu AGU12RLF Service Instruction page 34

Trouble shooting 6
INDOOR UNIT Error Method:
INDOOR UNIT
Indoor heat Ex.(Pipe) thermistor error
Detective Actuators:
Indoor unit Controller PCB
Heat Ex. 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 OK
Check Point 2 : Remove connector and check Thermistor resistance value
Check Point 2 :
Thermistor Characteristics (Approx. value)
Temperature (°F)
Resistance Value (k )
Temperature (°F)
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
(PIPE)
GRAY
GRAY
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 Heat Ex. Temperature Thermistor open or short-circuit is detected.
2.Thermistor failure
14°F 23°F 32°F
312.3 233.2 176.0
86°F 104°F 122°F
39.6 25.6 17.1
1 1
CN3
2 2
1
CN1
2
3. Controller PCB failure
41°F 50°F 68°F
134.2 103.3 62.9
140°F 144°F
11.6 10.4
02-09