Panasonic WH-UD30BE5-1 Service Manual page 46

16.5.3. Compressor Low Pressure Protection (H42)
Error code will not display (no OFF/ON Control Panel LED blinking) but store in EEPROM
Malfunction Decision Conditions:
During operation of heating and after 5 minutes compressor ON, when outdoor pipe temperature below -29°C or above 26°C is
detected by the outdoor pipe temperature sensor.
Malfunction Caused:
1. Dust accumulation on the outdoor unit heat exchanger.
2. Air short circuit at outdoor unit.
3. 2/3 way valve closed.
4. Faulty outdoor unit fan motor.
5. Refrigerant shortage (refrigerant leakage).
6. Clogged expansion valve or strainer.
7. Faulty outdoor pipe temperature sensor.
8. Faulty outdoor unit main PCB.
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