Fujitsu ASU 9RLF1 Service Instruction page 32

Trouble shooting 6
INDOOR UNIT Error Method:
INDOOR UNIT
Indoor unit Heat Ex. sensor 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 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 (°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)
BLACK
1 1
BLACK
2 2
CN4
BLACK
3 3
BLACK
4 4
If the voltage does not appear, replace Controller PCB.
Indicate or Display:
Refer to error code table.
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
THERMISTOR
(PIPE)
THERMISTOR
(ROOM TEMP.)
3. Controller PCB failure
41°F 50°F 68°F
134.2 103.3 62.9
140°F 149°F
11.6 9.7
02-09