Fujitsu AO G18LBCA Series Service Instruction page 52

Trouble shooting 22
OUTDOOR UNIT Error Method:
Heat Ex. Outlet Temp.
Thermistor Error
Detective Actuators:
Heat exchanger liquid temperature
thermistor
Forecast of Cause :
1. Connector connection defective, open
2. Thermistor failure
3. Main PCB failure
Check Point 1 : Check the connector connection and cable open
Connector connection state check
Cable open check
OK
Check Point 2 : Check the thermistor
Thermistor characteristics check (Disconnect the thermistor from the PCB and check.)
* For the thermistor characteristics, refer to the "Service Parts Information 8".
OK
Check Point 3 : Check voltage of Main PCB (DC5.0V)
Main PCB CN71:1-2 voltage value =5V
Remove the thermistor from Main PCB, check the voltage.
4 3 2 1
4 3 2 1
If the voltage does not appear, replace Main PCB
the check operation again.
Indicate or Display:
Error code : 73
Detective details:
Heat exchanger outlet temperature thermistor short or open detected
CN71
DC
, and execute
02-23
Outdoor unit : No indication