Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 53

4210 (UP): Compressor overcurrent interruption/Failure in 12 VDC
power supply circuit on power circuit board
Diagnosis of failure
Continued from the previous page.
Are they connected properly?
Check the operation of indoor/outdoor fan
motors.
Does it operate normally?
Check for indoor/outdoor short-cycle.
Are those units short-cycled?
Disconnect the compressor wiring from the outdoor
power circuit board, then check the voltage among each
phases U, V and W during test run (SW7-1 ON).
Are the voltage among the phases
U-V, V-W and W-U different?
Replace the outdoor multi controller circuit
board.
Does it operate normally?
OCH800A_53
No
Yes
No
Yes
Yes
(Short-cycled)
No
(Not short-cycled)
Make sure to perform a voltage check with
the same performing frequencies.
No
Yes
No
Yes
Connect the compressor wiring (U, V and W
phase) properly, then turn the power back ON.
Check the DC fan motor.
Remove factor(s) causing the short-cycle.
Replace the compressor.
Replace the outdoor power circuit board.
Complete
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