Fujitsu AS*G09KXCA Series Service Instruction page 55

Trouble shooting 18
OUTDOOR UNIT Error Method:
Outdoor Thermistor Error
Detective Actuators:
Outdoor unit Main PCB
Outdoor 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 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 OK
Check Point 3 : Check voltage of Main PCB (DC5.0V)
Make sure circuit diagram of outdoor unit and check terminal voltage at thermistor (DC5.0V)
BLACK
Thermistor (Outdoor temp.)
1 1
P5 2 2
BLACK
3 3
If the voltage does not appear, replace Main PCB.
Indicate or Display:
Indoor Unit :
Operation indicator : 7 times Flash
Timer indicator
Economy indicator: Continuous Flash
Error code : [ E: 74 ]
Detective details:
When Outdoor temperature thermistor open or short-circuit
is detected at power ON or while running the compressor.
2. Thermistor failure
-30 -20 -10 -5
224.3 115.2 62.3 46.6
20 30 40 50
12.6 8.0 5.2 3.5
02-22
: 4 times Flash
3. Main PCB failure
0 5
10 15
35.2 26.9 20.7 16.1
60 70 80
2.4 1.7 1.2