Fujitsu ASU18RMLQ Service Instruction page 45

Trouble shooting 12
OUTDOOR UNIT Error Method:
Compressor Temperature
Thermistor Error
Detective Actuators:
Outdoor Unit Main PCB Circuit
Compressor 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 (Rough 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 Compressor 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)
176 135 105 81.8
158°F 176°F 194°F 212°F
(70°C) (80°C) (90°C) (100°C)
8.78 6.31 4.61 3.43
1 2 1 2 1 2
CN23 CN22 CN21
02-19
68°F 86°F 104°F 122°F
(20°C) (30°C) (40°C) (50°C)
64.5 41.1 26.9 18.1
248°F 284°F 320°F 356°F
(120°C) (140°C) (160°C) (180°C)
1.98 1.21 0.77 0.51
140°F
(60°C)
12.5