Fujitsu ASU18RLF Service Instructions Manual page 42

Trouble shooting 19
OUTDOOR UNIT Error Method:
4-Way Valve Error
Detective Actuators:
Indoor Unit Controller PCB Circuit
Heat Exchanger Temperature Thermistor
Room Temperature Thermistor
4-way valve
Forecast of Cause :
1. Connector connection failure
5. 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 mis-wiring, reset the power.
OK OK
Check Point 2 : Check thermistor of Indoor unit
Isn't it fallen off the holder?
Is there a cable pinched?
>> Check characteristics of thermistor, (Refer to Trouble shooting 6,7),
If defective, replace the thermistor.
OK OK
Check Point 3 : Check the solenoid coil and 4-way valve
[ Solenoid coil ]
Remove CN500 from PCB and check the resistance value of coil.
Resistance value is about 1.4k
>> If it is Open or abnormal resistance value, replace Solenoid Coil.
[ 4-way valve ]
Check each piping temperature,
and the location of the valve by the temperature difference.
>> If the value location is not proper, replace 4-way valve.
OK OK
Check Point 4 : Replace Main PCB
If Check Point 1- 3 do not improve the symptom, replace Main PCB.
Indicate or Display:
Refer to error code table.
Detective details:
When the indoor heat exchanger temperature is compared with
the room temperature, and either following condition is detected
continuously two times, the compressor stops.
Cooling or Dry operation
[Indoor heat exchanger temp.] - [Room temp.] > 50degF
Heating operation
[indoor heat exchanger temp.] - [Room temp.] < -50degF
If the same operation is repeated 2 times,
the compressor stops permanently.
2. Thermistor failure 3. Coil failure
02-21
4. 4-way valve failure