Fujitsu AOTG30KMTC, Service Manual, Page: 66 / 199

2-15. E: 42. Indoor unit heat exchanger sensor error (Indoor
unit)
Indicator
Indoor unit
Operation indicator 4 time flash
Timer indicator 2 time flash
Economy indicator Continuous flash
Error code E: 42
outdoor unit
Refer to “Error code table (Outdoor unit: for 34 model
only)” on page 1
Detective actuator
Indoor unit controller PCB
When heat exchanger temperature thermistor open or
short circuit is detected.
Heat exchanger temperature
thermistor
Forecast of cause
Connector connection failure
Thermistor failure
Controller PCB failure
Check point 1. Check connection of connector
• Check if connector is loose or removed.
• Check erroneous connection.
• Check if thermistor cable is open
-> Reset power when reinstalling due to removed connector or incorrect wiring.
↓
Check point 2. Remove connector and check thermistor resistance value
• For the room thermistor resistance value, refer to "Thermistor resistance values"
on page 03-86.
• If thermistor is either open or shorted, replace it and reset the power.
↓
Check point 3. Check voltage of main PCB
Make sure circuit diagram of each indoor unit and check terminal voltage at thermis-
tor (DC 5.0 V).
BLACK
BLACK
1
2
4
CN1
BLACK
BLACK
3
1
2
4
3
Thermistor (Pipe temp.)
Thermistor (Room temp.)
If the voltage does not appear, replace main PCB.
↓
End
2-15. E: 42. Indoor unit heat exchanger sensor error (Indoor unit)
- (03-28) -
2. Troubleshooting with error code
TROUBLESHOOTING TROUBLESHOOTING