Fujitsu ASU18RMLQ Service Instruction page 36

Trouble shooting 3
INDOOR UNIT Error Method:
INDOOR UNIT
Room Temperature Thermistor Error
Detective Actuators:
Indoor Unit Control PCB(AS, AR) ,
Main PCB(AU) or Room Temperature
Thermistor
Forecast of Cause :
1. Connector connection failure 2.Thermistor failure 3. Control PCB (AS,AR),MainPCB (AU) 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
Check Point 2 : Check Point 2 : Remove connector and check Thermistor resistance value
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
Check Point 3 : 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)
GRAY
1
GRAY
2
BLACK
1
BLACK
2
If the voltage does not appear, replace Controller PCB(AS, AR), Main PCB(AU).
Indicate or Display:
Refer to error code table.
Detective details:
When Room Temperature Thermistor open or short-circuit is
detected at power ON.
32°F 41°F 50°F 59°F
(0°C) (5°C) (10°C) (15°C)
33.6 25.9 20.2
104°F 113°F 122°F
(40°C) (45°C) (50°C)
5.30 4.35 3.59
THERMISTOR
(PIPE TEMP.)
THERMISTOR
(ROOM TEMP.)
02-10
68°F 77°F 86°F
(20°C) (25°C) (30°C)
15.8 12.5 10.0 8.04
95°F
(35°C)
6.51