Panasonic CS-E12NKUAW, Service Manual

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15.4.27 F99 (Output Over Current Detection)
Malfunction Decision Conditions
During operation of cooling and heating, when an output over-current (18.5A) is detected by checking the current that
flows in the inverter DC peak sensing circuitry.
Malfunction Caused

DC peak due to compressor failure.

DC peak due to defective power transistor(s).

DC peak due to defective outdoor unit PCB.
Troubleshooting

Checking the power transistor

Never touch any live parts for at least 10 minutes after turning off the circuit breaker.

If unavoidable necessary to touch a live part, make sure the power transistor’s supply voltage is below 50V using
the tester.

For the UVW, make measurement at the Faston terminal on the board of the relay connector.
Tester’s negative terminal Power transistor (+) UVW Power transistor (-) UVW
Tester’s positive terminal UVW Power transistor (+) UVW Power transistor (-)
Normal resistance Several k Ω to several M Ω
Abnormal resistance 0 or ∞