Mitsubishi Electric NTXMSM36A142BA Technical & Service Manual page 79

Check code
4250
(U6)
Abnormal points and detection methods
If overcurrent of DC bus or compressor is detected 30 seconds after the
compressor starts operating. To determine the source of abnormality,
either the compressor or the power module, drive the power module
forcedly.
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Check the outdoor stop valve.
Is the stop valve (liquid/gas) fully
open?
Check whether the power supply voltage is
normal or not.
Is the power supply voltage normal?
Turn the power OFF to check for
looseness, disconnection or phases of the
compressor wiring.
Are the wirings normal?
Disconnect the wiring to check the power
module.
Does it operate normally?
OCHT810A
Power module trouble or overcurrent trouble
Diagnosis
Yes
Yes
Yes
Yes
Causes and checkpoints
Closed outdoor stop valve
Decrease of power supply voltage
Disconnection, looseness or conversed connection
of compressor wiring
Defective compressor
Defective outdoor power circuit board
Open the stop valve (liquid/gas) fully.
No
Ensure power supply from facility.
No
Connect the compressor wiring (U, V and
W phase) properly, then turn the power
No
back ON.
Replace the outdoor power circuit board
or outdoor multi controller circuit board
No
(Defective power circuit board).
Replace the compressor
(Defective compressor).
79
Remedy