What is the "W" terminal on the alternator for?

[redfred777]

I just replaced the alt on my 92' Eco Diesel, I didn't notice until it was
installed that it had no W post. when I went back to the parts store
they called the remanufacterer who said "don't worry about it, just tape
off the wire" As far as I can tell from the Bentley manual, it is a lead
for the tach(which i don't have).
   Is it OK to to operate it this way? It's been 2 days and seems ok.

[BlackTieTD]

correct, tach.
yep, you should be fine like that.