Panasonic CU-3E19RBU-5 Service Manual page 88

15.2.23 F99 (Outdoor Direct Current (DC) Peak Protection)
Malfunction Decision Conditions

During operation of cooling and heating, when an output over-current 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.
Abnormality Judgment:

Continuous happen for 7 times.
Troubleshooting
Get restarted and
measure the input
current.
Input current > 18.5A?
Yes
Is the refrigerant over
charged?
No
Check the compressor winding
resistance:
- Turn off the power and disconnect the
harnesses U, V, and W
- Measure the winding resistance
between U-V, V-W, and W-U
■ Checking the power transistor
● Never touch any live parts for at least 10 minutes after turning off the circuit breaker.
● If unavoidably necessary to touch a live part, make sure the power transistor's supply
● For the UVW, make measurements at the Faston terminal on the board or the relay
Tester's negative terminal
Tester's positive terminal
Normal resistance
Abnormal resistance
Caution
No
Replace the outdoor unit
Yes
Remove excess gas
voltage is below 50 V using the tester.
connector.
Power transistor (+)
UVW
For safety reason and to prevent component
breakdown, always switch off the power
before remove and connect the component.
PCB.
Are the compressor's
winding resistance (U-V,
V-W, or U-W) shorted?
No
UVW
Power transistor (+)
Several kΩ to several MΩ
0 or ∞
88
Yes
- Compressor defective due to
winding shorted
- Replace compressor
- Outdoor electronic circuit defect
due to power transistor short
- Replace the outdoor unit PCB
Power transistor (-)
UVW Power transistor (-)
UVW