Fujitsu ASU18RMLQ Service Instruction page 52

Trouble shooting 19
OUTDOOR UNIT Error Method:
Heat Sink Temperature
Thermistor Error
Detective Actuators:
Outdoor Unit Main PCB Circuit
Heat Sink 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 )
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 Sink Temperature Thermistor open or short-circuit is
detected at power ON or while running the compressor.
32°F 41°F 50°F 59°F
(0°C) (5°C) (10°C) (15°C)
16.1 12.4 9.73
140°F 158°F 176°F 194°F
(60°C) (70°C) (80°C) (90°C)
1.25 0.89 0.65
1 2 1 2 1 2
CN23 CN22 CN21
02-26
68°F 86°F 104°F
(20°C) (30°C) (40°C)
7.67 6.10
3.95 2.62
212°F 230°F 248°F
(100°C) (110°C) (120°C)
0.48 0.36 0.27 0.21
122°F
(50°C)
1.79