Fujitsu AOUG09LMAS1, Service Manual

Page: 51 / 134

2-14. E: 74. Outdoor temperature thermistor error (Outdoor unit)
Indicator Indoor unit
Operation indicator 7 time flash
Timer indicator 4 time flash
Economy indicator Continuous flash
Error code E: 74
Detective actuator
Outdoor unit main PCB When outdoor temperature thermistor open or short
circuit is detected at power on or while running the
compressor
Outdoor temperature thermistor
Forecast of cause
Connector failure
Thermistor failure
Main 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 outdoor temperature thermistor resistance value, refer to "Thermistor re-
sistance values" on page 03-40.
• 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 outdoor unit and check terminal voltage at thermistor
(DC 5.0 V).
NOTE: For details of thermistor connector, refer to "Wiring diagrams" in Chapter 2.
TECHNICAL DATA AND PARTS LIST on page 02-14.
If the voltage does not appear, replace main PCB.
↓
End
2-14. E: 74. Outdoor temperature thermistor error (Outdoor unit)
- (03-17) -
2. Troubleshooting with error code
TROUBLESHOOTING TROUBLESHOOTING