Fujitsu ASU18RMLQ Service Instruction page 37

Trouble shooting 4
INDOOR UNIT Error Method:
INDOOR UNIT
Indoor Heat Exchanger 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 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
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 Heat Exchanger 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)
176 134 103
104°F 113°F 122°F
(40°C) (45°C) (50°C)
25.6 20.8 17.1
THERMISTOR
(PIPE TEMP.)
THERMISTOR
(ROOM TEMP.)
02-11
68°F 77°F 86°F
(20°C) (25°C) (30°C)
80.3 62.9 49.7 39.6
95°F
(35°C)
31.7