Fujitsu ASU18RLB Service Instructions Manual page 33

Trouble shooting 6
INDOOR UNIT Error Method:
Indoor Heat Ex.(Pipe)
Thermistor Error
Detective Actuators:
Indoor unit Controller PCB
Heat Ex. temperature thermistor
Forecast of Cause :
1. Connector connection 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 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 Controller PCB (DC5.0V)
Make sure circuit diagram of indoor unit and check terminal voltage at Thermistor (DC5.0V)
THERMISTOR
(PIPE TEMP.)
BLACK
1
2
BLACK
3
THERMISTOR
(ROOM TEMP.)
If the voltage does not appear, replace Controller PCB.
Indicate or Display:
Outdoor Unit : No indication
Indoor Unit
ERROR CODE : [E : 42]
Detective details:
When Heat Ex. Temperature Thermistor open or short-circuit is detected.
2.Thermistor failure
14°F 23°F 32°F
312.3 233.2 176.0
86°F 104°F 122°F
39.6 25.6 17.1
RED
1
1 1
CN3
2
2 2
WHITE
3
BLACK
1 1
CN1
BLACK
2 2
: Operation lamp: 4 time Flash, Timer lamp: 2 time Flash
Economy lamp: Continuous flash.
3. Controller PCB failure
41°F 50°F 68°F
134.2 103.3 62.9
140°F 149°F
11.6 10.4
02-09