RBHouston@aol.com wrote:
> > The entire car is isolated from the ground by the rubber tires. All of the
> > electrical bits must therefore be grounded back to the negative terminal of
> > the battery so they will operate.
Although the rest of your point is accurate, this is a little
meaningless.
The "ground" that you are standing on is unrelated to chassis
ground in a car, so isn't a factor. If you could somehow
ground your radio in the car to the pavement it doesn't work
as an electrical ground to the circuit.
Note that this isn't true with houses, because the house
electrical circuit is grounded with a rod driven into the
earth. So the word "ground" actually means something, and you
could get some current to flow by taking a leg of your house wiring
and stabbing it into the earth.
> > If you disconnect the POS side, and then
> > drop anything metal on the POS terminal, and then allow it to touch almost
> > anything metal in the car, you will cause a short to Ground. If you
> > disconnect the NEG side, you are removing the ground path back to the
> > battery, so everything is safe from shorting.
> >
> > (I think)
>
> Uhhhhnooooooo....if you disconntect the Neg..gound side and the drop anything
> metal on the Neg terminal and then allow it to touch almost anything metal in
> the car...you are causing a completed circuit...
In your own words, "Uhhhhnooooooo" again...
Perhaps in a sense, but certainly not a dangerous one. You
are only reconnecting the original circuit, so the only current
that would flow would be things like clocks, radio preset memory,
door lights if a door is open, and so on.
Shorting that terminal to ground is the same as just hooking
it up again, no danger. If your wrench inadvertedly clicks against
the body while working on that terminal, you might hear the
clock tick, that's about it. ;>
Shorting the OTHER terminal to ground is spectacular and
often expensive.
More important is the order that the cables are
connected. If you connect the positive last or
disconnect it first then your wrench is a lightning
rod for everything around, an accident waiting to
happen.
If you connect the ground circuit last, or disconnect
it first, you can crack it around and click it against
the bonnet with impunity. Just use a wrench short
enough to not reach the positive terminal and you are
safe.
I suspect the "preferred" method of attaching a quick
connect grew out of this method.
--
Trevor Boicey, P. Eng.
Ottawa, Canada, tboicey@brit.ca
ICQ #17432933 http://www.brit.ca/~tboicey/
Live from the Prestone Zone.
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