I wonder if the fan's fed from somewhere else on yours.

Fanuc OTA diagrams can be found at http://denfordata.com/bb/viewtopic.php?f=15&t=2337
However, I just looked at this set - http://denfordata.com/bb/viewtopic.php?f=15&t=2508 and the spindle fan is single phase powered via Fuse 4. However those machines appear to have 3 phase + Neutral input, whereas the older ones were only pure 3 phase. Do you know what power input your machine has?