Mitsubishi Heavy Industries SRK20ZD-S1 Technical Manual page 51

Serial signal transmission error
Does error persist after power
reset?
Is there any wrong connection on
indoor/outdoor unit wiring?
Is DC 0~Approx. 12V detected
between 2~3 terminals on
indoor unit terminal block?
Is DC 0~Approx. 12V detected
between2~3 terminals on
outdoor unit terminal block?
Is AC 220/230/240V applied
between 1~2 on the outdoor side
terminal block?
Is there any problem on the power
supply line (fuse, reactor,
capacitor, etc.)?
Indoor fan motor error
Is connector connection good?
Is voltage applied to fan motor?
Rotor lock
YES
YES
YES
YES
YES
YES
Defective outdoor unit PCB
YES
YES
Defective fan motor
Is output voltage applied to all 3
phases of power transistor?
YES
Inspect compressor.
[Wiring error including power cable, defective indoor/
outdoor unit PCB, error on power supply system]
NO
Trouble by transient cause, not unit trouble.
NO
Correct improper wire connection on indoor/
outdoor unit.
NO
Defective indoor unit PCB
NO
Check crossover wires.
NO
Defective indoor unit PCB. Check crossover wires.
NO
Replace fuse, reactor or capacitor.
NO
Correct connector
connection.
NO
Defective indoor unit
PCB
NO
Defective inverter
¡ Check compressor wiring visually.
¡ Check insulation resistance. (1 MΩ or over)
¡ Check coil wire resistance. (Few Ω)
49
- -
[Defective fan motor,
defective PCB]
[Compressor defect, outdoor
unit circuit defect]
If check results are normal,
compressor is locked.