14.4.23 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
When F99 indication happens
Get restarted and measure the input
current.
Input current > 18.5A?
Check the compressor winding resistance:
•
Turn off the power and disconnect
the harness U, V and W
•
Measure the winding resistance
between U-V, V-W and W-U.
Are the compressor's winding resistance
(U-V, V-W or U-W) shorted?
•
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
Tester's positive terminal
Normal resistance
Abnormal resistance
NO
YES
YES
NO
Power transistor (+)
UVW
For safety reason and to prevent component
breakdown, always switch off the power
before remove and connect the component.
•
Replace the outdoor unit PCB.
•
Compressor defective due to winding
shorted.
•
Replace compressor
•
Outdoor electronic circuit defect due
to power transistor short
•
Replace the outdoor unit PCB.
UVW
Power transistor (-)
Power transistor (+)
Several kΩ to several MΩ
0 or ∞
66
UVW
UVW
Power transistor (-)