Fujitsu ASU18RLF Service Instructions Manual page 34

Trouble shooting 11
OUTDOOR UNIT Error Method:
Discharge Thermistor Error
Detective Actuators:
Outdoor Unit Main PCB
Discharge Pipe 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 )
Temperature (°F )
Resistance value (k )
Temperature (°C )
Temperature (°F )
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)
BROWN
BROWN
BLUE
BLUE
BLACK
BLACK
BROWN
BROWN
If the voltage does not appear, replace Main PCB.
Indicate or Display:
Refer to error code table.
Detective details:
When Discharge Pipe Temperature Thermistor open or short-circuit
is detected at power ON or while running the compressor.
2. Thermistor failure
0 5 10
32 41 50
168 130 102 80.5
70 80 90
158 176 194
8.9 6.4 4.6
THERMISTOR
( COMPRESSOR TEMP. )
THERMISTOR
( OUTDOOR TEMP. )
THERMISTOR
( HEAT EXCHANGER )
THERMISTOR
( DISCHARGE PIPE )
3. Main PCB failure
15 20 30 40
59 68 86 95
63.9 41.1 27.1
100 120
212 248
3.4 2.0
02-13
50 60
122 140
18.3 12.6