OCH790 _59
5106 (U4): Ambient temperature thermistor (TH7) open/short
Abnormal points and detection methods
TH7 is found to be open/short
Open:
−40°C [−40°F] or less
Short:
90°C [194°F] or more
TH7:
Thermistor <Ambient>
Causes and checkpoints
• Disconnection or contact failure of connectors
•
Faulty thermistor
•
Defective outdoor multi controller circuit board
The black square (■) indicates a switch position.
Diagnosis of failure
Connect the wiring/connector properly.
Replace it in the case of breakage.
Replace the thermistor.
Replace the outdoor multi controller circuit board
(Malfunction of thermistor circuit).
No abnormality
(A connector contact failure is suspected.)
Check the wiring and connector connection of
TH7.
Disconnect the connector to check the resis-
tance of TH7 using a multimeter.
Check the temperature of TH7.
The detected temperature of TH7 can be displayed by an
operation of SW1 on the outdoor multi controller circuit board.
Is there any abnormality such as
disconnection, looseness or break-
age?
Is the detected resistance normal?
Is the detected temperature normal?
ON
OFF
1 2 3 4 5 6 7 8
SW1 Setting
Display on LED1, 2
Unit
–99.9–999.9
°C
Yes
No
No
Yes
Yes
No
