Fujitsu ASU7RLF1 Service Instructions Manual page 56

Trouble shooting 19
OUTDOOR UNIT Error Method:
Outdoor 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 miss-wiring, reset the power.
OK
Check Point 2 : Remove connector and check Thermistor resistance value
Thermistor Characteristics (Approx. value)
Temperature(°F)
Resistance Value (k )
Temperature(°F)
Resistance Value (k )
If Thermistor is either open or shorted, replace it and reset the power.
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)
1
CN24
BLACK
2
WHITE
1
CN25
BLACK
2
BLACK
1
CN26
BROWN
GREEN 2
1
CN23
BLUE
BLUE
2
1
CN22
BLACK
2
RED
1
CN21
BROWN
YELLOW
2
If the voltage does not appear, replace Main PCB.
Indicate or Display:
Outdoor Unit :
Indoor Unit
ERROR CODE : [E : 74]
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
115 62.3 46.6
86°F 104°F 122°F
7.97 5.18 3.45
THERMISTOR
(PIPE MID)
THERMISTOR
(HEAT SINK)
THERMISTOR
(COMPRESSOR)
THERMISTOR
(OUTDOOR)
THERMISTOR
(PIPE)
THERMISTOR
(DISCHARGE)
LED 1 : 4 time Flash
: Operation lamp: 7 time Flash, Timer lamp: 4 time Flash
Economy lamp: Continuous flash.
32°F 41°F 50°F
35.2 26.9 20.7
140°F 158°F
2.36 1.65
02-24
59°F 68°F
16.1 12.6