Insufficient Refrigerant Amount Or Detection Of Service Valve Closure - Mitsubishi Heavy Industries FDT71VNXWVH Service Manual

Error code
Indoor control PCB
Remote control:
E57
Outdoor control PCB
Outdoor inverter
1. Applicable model
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).
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
(or main) PCB
• Insufficient refrigerant
amount
Note: Insufficient refrigerant amount preventive control makes compressor stopped, if it judges insufficient refrigerant amount by detecting the
temperature difference between indoor heat exchanger (Thi-R) and return air temperature (Thi-A) for 1 minute 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]
LED Green
Keeps flashing
Keeps flashing
Yellow LED
PCB
Keeps flashing
5. Troubleshooting
service valve fully
opened?
connections of indoor
heat exchanger and/or return air
temperature sensor
connectors OK?
characteristics of indoor heat
exchanger and/or return air
temperature sensor
Is the low
pressure during operation
Indoor heat exchanger, return air temperature sensor
Temperature-resistance characteristics
(Broken wire)
15
10
5
(Short-circuit)
Red
Content
Stays OFF
Insufficient refrigerant amount
1-time flash
or detection of service valve closure
Diagnosis
Is the
NO
YES
Are the
NO
YES
Are the
NO
OK?
YES
NO
normal?
YES
5k at 25°C
0 10 20 30 40 50
Temperature (°C)
117
- -
'19 • PAC-SM-332
Countermeasure
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 (or main)
PCB ➞ Replace. (Defective
indoor heat exchanger,
return air temperature
sensor input circuits)