I read an interesting article in Automotive Engineering
magazine last month on this topic. It seems that some of
the electric-fan cars now have "current recovery" circuits
being added to the fans so that when they are OFF, but
spinning in the wind, they can put some current back into
the electrical system, lightening the alternator's load, thus
improving overall efficiency, etc., etc.
I know that my added-on electric fan will light up the
'manual override' lighted switch I installed on the dash
while I'm on the highway. Why not save it?