Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 60

5102 (U4): Suction pipe temperature thermistor (TH6) open/short
Abnormal points and detection methods
TH6 is found to be open/short.
(The open/short detection is disabled for 10 seconds to 10
minutes after compressor starts, during defrosting opera-
tion, or for 10 minutes after returning from the defrosting
operation.)
Open:
−40°F (−40°C) or less
Short:
194°F (90°C) or more
TH6:
Thermistor <Suction pipe>
Diagnosis of failure
Check the wiring and connector connection of
TH6.
Is there any abnormality such as
disconnection, looseness or break-
age?
Disconnect the connector to check the resis-
tance of TH6 using a multimeter.
Is the detected resistance normal?
Check the temperature of TH6.
Is the detected temperature normal?
OCH800A_60
<Detected in outdoor unit>
Yes
No
No
Yes
The detected temperature of TH6 can be displayed
by an operation of SW1 on the outdoor multi
controller circuit board.
ON
OFF
1 2 3 4 5 6 7 8
No
Yes
Causes and checkpoints
• Disconnection or contact failure of connectors
• Faulty thermistor
• Defective outdoor multi controller circuit board
Connect the wiring/connector properly.
Replace it in the case of breakage.
Replace the thermistor.
SW1 Setting Display on LED1,2
Unit
-99.9–999.9 °F
Replace the outdoor multi controller circuit board
(Malfunction of thermistor circuit).
No abnormality
( A connector contact failure is suspected.)
The black square (■) indicates a switch position.