Mitsubishi Electric MUZ-LN25VGHZ Service Manual page 38

12-5. TROUBLESHOOTING FLOW
A How to check inverter/compressor
Disconnect the connector between the compressor
and the power module (IC700).
Check the voltage between terminals.
Are the voltages balanced?
Yes
Check the compressor.
B Check of open phase
● With the connector between the compressor and the power module (IC700) disconnected, activate the inverter and check if
the inverter is normal by measuring the voltage balance between the terminals.
Output voltage is 50 - 130V. (The voltage may differ according to the tester.)
<< Operation method>>
Start cooling or heating operation by pressing EMERGENCY OPERATION switch on the indoor unit. (TEST RUN OPERA-
TION: Refer to 9-3.)
<<Measurement point>>
At 3 points
BLK (U)-WHT (V)
BLK (U)-RED (W)
WHT(V)-RED (W)
NOTE: 1. Output voltage varies according to power supply voltage.
2. Measure the voltage by analog type tester.
3. During this check, LED of the inverter P.C. board fl ashes 9 times. (Refer to 12-6.1.)
C Check of compressor
Refer to 12-5. "Check of compressor
winding".
Is the compressor normal?
Refer to 12-5. "Check of compressor
operation time".
Does the compressor operate continuously?
OK
OBH768
No
Measure AC voltage between the lead wires at 3 points.
No
Yes
No
Yes
See 12-5. "Check of open phase".
Replace the inverter P.C. board.
See 12-5. "Check of compressor".
Replace the compressor.
Refer to 12-5. "Check of compressor start failure".
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