[ihc] "Free" Power from an electric fan?

[Tom Mandera <tsm1@xxxxxxxxx>]

David Bongo wrote:

> So, the general consensus seems to be to leave the stock fan setup in
> place and see what happens.  I'll think about it.  I don't really have
> the money, but it just seems to me that since it's under $100 for the
> auxiliary electric fan, it's worth considering.  (That's pricing out a
> Perma-Cool fan.  Something else will be much cheaper, I'm sure.)  I
I'd think twice about an electric fan on your Postal.

Remember TANSTAAFL?

Sure, you remove the mechanical drag on the waterpump by removing the 
mechanical fan.  Great!

But you've added the electrical drain of an electric fan to the system. 
 How do you replace the electrical power you're using?  Oh, the 
alternator does that!

Ever have an alt belt start squealing when you suddenly turned on the 
high-beams/heater at once and the belt isn't tight enough?  It squeals 
because the more electrical loads you put on the system, the more *HP* 
it takes to turn the alternator and generate juice.

Thus you "save" power by ditching the fixed fan, but you "lose" power by 
upping the alternator's power robbing thirst.

You do "save" a little, since the electrical fan only cycles on when you 
"need" it, and you may not need it all of the time.  Of course, a good 
clutched mechanical fan does most of that, too.

I'd be very concerned with your type of use, though.

I put a 90 (94?) amp Delco 12si alternator on my Travelette when I put 
my engine in last summer, along with a Ford Taurus electric fan.

This past weekend we went to Bozeman, MT's "Wild West Winterfest" to do 
some ice-racing in the race Scout.

We used the Travelette to haul the Scout down.

While idling before and after the race with the heater fan on, the 90amp 
Delco was more or less keeping up, according to the voltmeter.

Then the Taurus electric fan kicked on.  The heater blower made a lower 
pitched noise and slowed down a little, and the voltmeter dipped.  The 
alternator wasn't making enough juice any more.

At night, under similar conditions, the headlights/dashlights would dim.

This, with a high quality 90amp alternator that makes pretty good output 
even at idle.

Running down the highway at 3500rpm on the way home, I can run the 
electric fan non-stop, the heater on high, high-beams on the headlights, 
use the trailer brake controller as necessary, *AND* crank the tunes 
with no ill effects.

But idling, in stop-and-go situations?  I think the mechanical fan would 
be a better choice.