1)  Release the UVW connector. Measure the resistance of U-V, U-W, V-W. If the resistance is not 
equal to each other, the fan motor must has problems and need to be replaced. Otherwise, go to 
step 2. 
2)  Power  on and  when  the unit is  in  standby,  measure  the voltage  of  pin4-5  in  feedback signal 
connector. If the value is not 5V, change the PCB. Otherwise, go to step 3. 
3)  Rotate the fan by hand, measure the voltage of pin1-5, pin 2-5 and pin 3-5 in feedback signal 
connector. If any voltage is not positive voltage fluctuation, the fan motor must has problems and 
need to be replaced.