NO
NO
NO
Is the voltage DC 15 V on the
control PCB side after the contact
(CNI3 or 1) has been removed?
YES
YES
YES
Is the voltage DC 15 V between the
contacts CNI4:2-3 on the inverter
PCB?
Replace the inverter PCB.
Defective cable between control
PCB and inverter PCB.
Is the voltage DC 15 V at the fan
motor’s contact?
Replace the fan motor.
Replace the control PCB.