Midea MSH-07CRN1, MSH-07HRN1, MSH-09CRN1, MSH-09HRN1, MSH-12CRN1, MSH-12HRN1 Manual page 357

8.3 Diagnostic Chart
8.3.1 After energizing, no indicator is lighted and the air conditioner can't be operated.
After energizing, the air conditioner can't be operated
Check if AC220V power supply outputs to Indoor PCB.
Check if AC220V exists at the primary coil of transformer.
Check if AC14.5V exists at the secondary coil of transformer.
Take off the secondary plug of transformer, and then check if
AC14.5V exists at the secondary coil of transformer.
8.3.2 Resetting phenomenon often occurs during operation. (That is automatically entering to the status when
power is on.)
The reason is that the instantaneous voltage of main chip is less than 4.5V. Check according to the following procedure:
Resetting phenomenon often occurs during operation.
Yes
After changing Indoor PCB, check if the failure releases
After changing indoor fan motor, check if the failure releases
Power supply circuit has problems.
Yes
Yes
No
No
The transformer is defective.
No
No
No
Yes
Yes
.
Yes
.
27
Indoor PCB is defective
Indoor PCB is defective
Indoor PCB is defective