No
Yes
All lamps flashing at 5Hz
Judge 1: The PRO terminal on PCB of indoor unit without connecting to grounding wire
Validate: Check whether the PRO terminal on PCB of indoor
unit without connected to grounding wire.
Connect it to grounding wire.
Judge 2: Optical coupler on PCB malfunction
Validate: Check whether the Optical coupler is normal. Replace optical coupler
Replace indoor PCB.