Fujitsu ASU18RMLQ Service Instruction page 38

Trouble shooting 5
OUTDOOR UNIT Error Method:
Outdoor Heat Exchanger Temperature
Thermistor Error
Detective Actuators:
Outdoor Unit Main PCB Circuit
Heat Exchanger Temperature Thermistor
Forecast of Cause :
1. Connector connection failure 2.Thermistor failure 3. Main 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 )
If Thermistor is either open or shorted, replace it and reset the power.
OK OK
Check Point 3 :
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)
1 2 1 2
CN25 CN26
If the voltage does not appear, replace Main PCB.
Indicate or Display:
Refer to error code table.
Detective details:
When Heat Exchanger Temperature Thermistor open or short-circuit is
detected at power ON or while running the compressor.
14°F 23°F 32°F 41°F
(-10°C) (-5°C) (0°C) (5°C)
27.5 20.9 16.1 12.4
1 2 1 2 1 2
CN23 CN22 CN21
02-12
50°F 59°F 68°F 77°F
(10°C) (15°C) (20°C) (25°C)
9.73 7.67 6.10 4.89
86°F
(30°C)
3.95
DC