Panasonic WH-UD28AE Service Manual page 53

16.5.11. Outdoor Low Pressure Abnormality (H63)
Malfunction Decision Conditions:
During operation of heating, the outdoor low pressure sensor output signal is 0Vdc or 5Vdc.
Malfunction Caused:
1. Faulty connector connection.
2. Faulty sensor.
3. Faulty PCB.
Abnormality Judgment:
Continue for 5 seconds (but no judgment for 5 minutes after compressor startup/restart).
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