Panasonic WH-UD30BE5-1 Service Manual page 57

16.5.14. Compressor Overheating (F20)
Malfunction Decision Conditions:
During operation of heating, when temperature above 112°C is detected by the compressor tank temperature sensor.
Malfunction Caused:
1. Faulty compressor tank temperature sensor.
2. 2/3 way valve closed.
3. Refrigerant shortage (refrigerant leakage).
4. Clogged expansion valve or strainer.
5. Faulty outdoor unit PCB.
6. Faulty compressor.
Abnormality Judgment:
Continue 4 times in 30 minutes.
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