Mitsubishi Electric FR-A700 Instruction Manual page 710

Useful functions
Cooling fan life display
The cooling fan speed of 50% or less is detected and "FN" is displayed on the operation panel
(FR-DU07) and parameter unit (FR-PU04/FR-PU07). As an alarm display, Pr. 255 bit 2 is turned
on and also an alarm is output to the Y90 signal.
NOTE
When the inverter is mounted with two or more cooling fans, the life of even one cooling fan
is diagnosed.
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Parameter