RE>ignition switch and seat belts            11/8/95

>From: jms@ludwig.att.com
I agree with Mark McCulley and Jim Davis that a new ignition
switch will help with starting . . . [deleted]. . .
Must of been the one that carried all the juice to the starter.
Well "all the juice" in a six volt system is kinda relative.

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Actually, this last statement is a very critical one to understand.  My
interpretation of it is that John ment that "all the juice" in a minimal
context.  Actually, in a 6 volt system, the "juice" (which I think of as amps)
is really twice that of a 12 volt system, where the wattage or power to do
work like turn the starter, headlights, etc is the same.  Electrical power is
measured in watts.  Watts are volts times amps.  Therfore, for a fixed
wattage, the 12 volt system will draw half the amps of a 6 volt system.

Suppose  you have two identical cars, one wired for 6 volts and the other for
12 volts.  Every other aspect is the same - same wattage headlights, same
compression on the engine for the starter to work against, etc.  The reason
that they went to 12 volts from 6 was that by doubling the voltage, they could
cut the current draw in half and still have the same wattage available to run
lights, starters, powers, etc.  By cutting the current draw in half, the size
of the wires carrying the power could be made of a smaller gauge because they
only had half the current to carry.  This saved copper (read as weight and $
and reduced the voltage drop between battery and load due the resistance of
the wire inbetween  (can get serious with 100 amp starter loads in cold
temps)) .  Another benefit is that by reducing  the current you are trying to
switch on/off, you prolong the life of switch contacts -- the greater the
current, the greater the arcing and the faster the contacts will wear out.  A
couple of major places for this are in the ignition circuit (ignition switch
and distributor points) as well as arcing at any motor's brushes.  Thus, in a
6 volt VW, you can expect heavier and or faster wear of any kind of electrical
switching contact compared to a 12 volt system..