Midea MSE-18HRN1-MQ8W - 11.3 Diagnostic chart

Service manual
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11.3 Diagnostic chart
After energizing, no indicator is lighted and the air conditioner can’t be operated.
For the 9K and 12K models:
Be sure all the wires(including power wires and connection wires)
is OK
Check if AC 115V (or 208-230V) power supply outputs to outdoor
PCB
Check if AC 115V (or 208-230V) exists at primary coil of
transformer
Check if AC 12V and AC 35V (+5%) exist at second coil of
transformer in the outdoor PCB
Outdoor PCB is defective
Yes
Yes
No
Take off the secondary plug of transformer, and then check if AC
12V and AC 35V (+5%) exist at secondary coil of transformer
No
Transformer is defective
No
Check if DC 35V exists between 2 and 3 on the indoor
terminal and DC 12V between 3 and 4
No
Indoor PCB is defective
Check if DC 35V exists at CN6 and 12V at CN3
Yes
No
Yes
No
Change good ones
Yes
Uncertain problem on indoor PCB, change it and
check again
Yes
Outdoor PCB is defective
Yes