Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 52

4210 (UP): Compressor overcurrent interruption/Failure in 12 VDC
power supply circuit on power circuit board
Abnormal points and detection methods
• Overcurrent of DC bus or compressor is detected 30 or
more seconds after the compressor starts the opera-
tion.
• 12 VDC power is not supplied from the 12 VDC supply
circuit on the power circuit board.
Diagnosis of failure
Which sub code is displayed?
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?
Check if the model selection switches are set
correctly on the indoor controller board or outdoor
multi controller circuit board.
Are they set properly?
Turn the power OFF to check for looseness,
disconnection, or wrong phases of the compres-
sor wiring.
Continue to the next page.
OCH800A_52
7
8
The sub codes are displayed by an operation of
SW1 on the outdoor multi controller circuit board.
SW1 Setting
ON
OFF
1 2 3 4 5 6 7 8
No
Yes
No
Yes
No
Yes
Causes and checkpoints
• Closed outdoor stop valve
• Decrease of power supply voltage
• Looseness, disconnection, or wrong phase of compres-
sor wiring connection
• Model selection error on indoor controller board or out-
door multi controller circuit board
• Defective compressor
• Defective outdoor power circuit board
• Defective outdoor multi controller circuit board
• Malfunction of indoor/outdoor unit fan
• Short-cycle of indoor/outdoor unit
Replace the outdoor power circuit board
(Defective outdoor power circuit board).
Display on LED1,2
1 2 3 4 5 6 7 8
7: 12 V power supply circuit trouble
8: Overcurrent trouble
Open the stop valve (liquid/gas) fully.
• Check the looseness, disconnection, or
breakage of compressor wiring.
• Ensure power supply from the facility.
(Check for power supply open phase.)
Set the model selection switches correctly.
Chart 1 of 2