Fujitsu ASU18RMLQ Service Instruction page 40

Split type room air conditioner
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Trouble shooting 7
OUTDOOR UNIT Error Method:
INDOOR UNIT
Outdoor Temperature
Thermistor Error
Detective Actuators:
Outdoor Unit Main PCB Circuit
Outdoor 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 Outdoor Temperature Thermistor open or short-circuit is
detected at power ON or while running the compressor.
- 4°F
14°F
23°F
(-20°C)
(-10°C)
(-5°C)
115
62.3
46.6
86°F
104°F
122°F
140°F
(30°C)
(40°C)
(50°C)
(60°C)
7.97
5.18
3.45
1 2
1 2
1 2
CN23
CN22
CN21
02-14
32°F
41°F
50°F
59°F
(0°C)
(5°C)
(10°C)
(15°C)
35.2
26.9
20.7
16.1
158°F
(70°C)
2.36
1.65
68°F
(20°C)
12.6

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