Hi Warren, you asked
> Fellow Scions,
>
> The recent cooling fan/generator/alternator thread brought
> back a question that I have wondered about for years: Does
> increasing electrical load really result in increased load
> on a generator/alternator, and therefore in increased gas
> mileage? Please hear me out before you answer, not because
> I'm right, but because I want a specific question answered.
> My argument is strictly intuitive, as I have no formal
> electrical education. Here goes: A generator consists of an
> armature (a metal shaft covered with wires) rotating between
> two magnets. There's no physical contact (other than
> brushes). How, therefore, can increased load make the
> armature harder to rotate? My intuition has always told me
> that a certain amount of electricity will be produced by
> this arrangement, and any excess beyond what's needed is
> (forgive me, this is all intuitive) bled off somehow, by
> sending it to ground.
>
How ? I'll need to leave that one to those better qualified, but here's
another example: When jump-starting a car, have you noticed that when
you make the final connection to ground, the engine speed of the car
that's providing the jump slows down due to the added load of charging
the dead battery ? That added electrical load is a drain on the power
output, horse-power output that is, available from the engine, as noted
by Dave M., Dan M., Trevor B. and probably others (please forgive any
omission here - and I want to thank you all for the free engineering
lessons, I am happily less ignorant than I was before this thread !).
> Related question: When I have my air conditioning on in the
> car, and I turn the temperature dial towards warmer, does
> the A/C compressor therefore start working less hard, and my
> gas mileage goes up, or does the compressor work just as
> hard, but the cool air get mixed with warm uncooled air in
> order to warm the air coming out of the vent?
>
The A/C clutch is either on or off, you can even watch it engage on
its pulley, driven by one of the V-belts. Most A/C controls will blend
cool air with warm to give you the desired interior temperature, so you
are correct in the latter part, above. The A/C compressor just has one
operating mode, as far as I know, but its output can be moderated by
varying fan speeds, or blending in outside air.
> I somebody can explain this in simple terms, I would
> appreciate it. You will have cleared up one of the mysteries
> of the universe for me.
>
> Warren Allen
> 1960 TR3A (And no, it doesn't have A/C. That question
> concerns a BAC (Big American Car.)
Hope the above helps explain what you were wondering about, and I can
sympathize with the BAC aspect, I am trying to get an old Delco/GM
air conditioner going again, after years of sitting open with a broken
high-pressure pipe off the compressor. I'm learning that there is a
dessicator to consider, a receiver-dryer, corrosion in the evaporator,
small screens to unplug, compressor oil to replace, etc., etc.,etc...
Best regards.
Tom Tweed
SW Ohio
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