Mitsubishi FDT71VH - Page 127

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126
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'20 • PAC-SM-351
E57
1. Applicable model
5. Troubleshooting
Diagnosis Countermeasure
NO
YES
NO
YES
Is the
service valve fully
opened?
Are the
connections of indoor
heat exchanger and/or return air
temperature sensor
connectors OK?
NO
YES
NO
YES
Are the
characteristics of indoor heat
exchanger and/or return air
temperature sensor
OK?
Is the low
pressure during operation
normal?
Indoor heat exchanger, return air temperature sensor
Temperature-resistance characteristics
15
10
5
010304020 50
Temperature sensor resistance (k
Ω)
Temperature (°C)
5kΩ at 25°C
(Broken wire)
(Short-circuit)
For the characteristics of indoor heat
exchanger,return air temperature sensor,
see the following graph.
Open fully.
Correct indoor heat
exchanger, return air
temperature sensor
connector connections.
Defective indoor heat
exchanger, return air
temperature sensor
➞
Replace.
Charge refrigerant.
Defective indoor unit
control PCB
➞
Replace.
(Defective indoor heat
exchanger, return air
temperature sensor input
circuits)
2. Error detection method
• Judge insufficient refrigerant
amount by detecting the
temperature differnce between
indoor heat exchanger (Thi-R)
and indoor return air (Thi-A).
• It detects at initial startup in
cooling or dehumidifying
mode after power ON.
3 . Condition of error displayed
Anomalous stop at initial
detection
4. Presumable cause
• Defective indoor heat
exchanger temperature sensor
• Defective indoor return air
temperature sensor
• Defective indoor unit control
PCB
• Insufficient refrigerant
amount
Note: Insufcient refrigerant amount preventive control makes compressor stopped, if it judges insufcient refrigerant amount by detecting the
temperature difference between indoor heat exchanger (Thi-R) and return air temperature (Thi-A) for 5 minutes after compressor ON in
cooling or dehumidifying mode and for 9 minutes after compressor ON in heating mode. [ in cooling mode: (Thi-A)-(Thi-R)<4degC, in
heating mode: (Thi-R)-(Thi-A)<4degC]
Error code
Remote control:
LED Green Red
Outdoor control PCB
Outdoor inverter
PCB
1-time flashKeeps flashing
Indoor control PCB
Stays OFFKeeps flashing
Content
Keeps flashing
Yellow LED
Insufcient refrigerant amount
or detection of service valve closure