Midea M2OC-18HFN1-M Service Manual page 45

9.4.1.3 zero-crossing signal error diagnosis and solution.
Malfunction decision
conditions
Supposed causes
Trouble shooting:
Check if the connections and
power supply is normal?
Yes
Indoor main PCB is
defective. Replace indoor
main PCB.
When PCB does not receive zero crossing signal feedback for
4 minutes or the zero crossing signal time interval is abnormal.
● Connection mistake
● PCB faulty
Correct the connections. Turn on the
No
unit when the power supply is good.