Panasonic CS-E18NKUA Service Manual page 59

15.4.13 F90 (Power Factor Correction Protection)
Malfunction Decision Conditions
During startup and operation of cooling and heating, when Power Factor Correction (PFC) protection circuitry at
the outdoor unit main PCB senses abnormal high DC voltage level.
Malfunction Caused
DC voltage peak due to power supply surge.
DC voltage peak due to compressor windings not uniform.
Faulty outdoor PCB.
Troubleshooting
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