Mitsubishi Electric PUMY-P36NKMU3 Technical & Service Manual page 69

Check code
4220
Primary current sensor error/Power synchronization signal error
(U9)
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting
any connectors, or replacing boards.
Continued from the previous page.
7,8
Check the power supply voltage on the terminal block
of the outdoor unit.
Check the bus voltage read by the microprocessor
with an operation of SW1 on the outdoor multi
controller circuit board.
Is the power supply normal?
Check the bus voltage at the test points
below on the outdoor power circuit board
using a multimeter.
Test points: CNDC 1–3pin
Is the bus voltage normal?
OCH733
Voltage shortage/Overvoltage/PAM error/L1 open-phase/
Diagnosis
6
Yes
Yes
Yes
The black square (■) indicates a switch position.
No Check the power supply facility.
The bus voltage can be displayed by an
operation of SW1 on the outdoor multi
controller circuit board.
SW1 Setting
Display on LED1,2
ON
0–9999
OFF
1 2 3 4 5 6 7 8
No
Check the power supply facility.
Check the resistor connected to 52C relay
and reactor. Replace it if the resistor is
broken. Replace the outdoor power circuit
No
board if the resistor is not broken.
Operate the unit and check if the problem
occurs again.
69
Chart 2 of 2
Remedy
Correct the CN5 wiring.
Unit
V