You are correct the alt turns on and off but it is based on the state of the battery, not the total vehicle draw, this happens regardless of the presence of an electric fan. But since the alternator produces a constant output, when engaged, regardless of the draw on the battery (which in this system acts like a huge capacitor) the only thing that would posibily change is the amount of times the alt is charging and possibly the duration, And that is difficult to control. So yes if the alt comes on in the 15+ seconds you are going down the track you will lose power, a negligable amount but a net loss. However, you run that risk w/o an electric fan.
I'm probably missing something else
but I'm sure someone will straighten me out. And I humbly aplogize for the above oversight of the fact the alt does turn on and off, so to speak.
