Mitsubishi Electric NTXMSM36A142BA Technical & Service Manual page 75

Check code
4210
12 VDC power supply circuit on power circuit board
(UP)
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
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?
OCHT810A
Compressor overcurrent interruption/failure in
Diagnosis
Yes
Yes
(short-cycled)
(no short-cycle)
No
Make sure to perform a voltage
check with the same performing
frequencies.
Yes
Yes
Connect the compressor wiring (U, V and
W phase) properly, then turn the power
No
back ON.
No
Yes
No
No
Replace the outdoor power circuit board.
75
Chart 2 of 2
Remedy
Check the DC fan motor.
Resolve the short-cycle.
Replace the compressor.
Complete.