Re: Which battery lead to disconnect?

[greg@domain.elided]

It has to do with DC electricity. With a few exceptions, most cars have a
negative ground (hopefully I don't have this reversed, I'm sure I'll be
promptly corrected if I am). That means almost every metal surface in the
car is tied together and ultimately is connected to the negative post of
the battery.

When the negative post of the battery is connected to the car and your
working in areas that carry current if you get across the hot wire and
touch just about any part of the car with your metal tool you'll complete
the circuit and see sparks fly.

Disconnecting the negative post of the battery means your reduce the
chances of that kind of accident from happening.

At least that's my understanding. I know there are also other reasons
besides safety, but safety is the most common reason that I know of.

On Sun, 12 Jan 2003, John Fielding wrote:

> Esteemed Digestables,
>
> I have often been puzzled by books recommending one to disconnect the negative lead from
> the battery before working on the vehicle.  I have tried to fathom out the logic why it
> must be the negative lead and not the positive.  If any one has a definitive article which
> explains why this should be so I would appreciate knowing about it.
>
> I have an alternative theory, but I would like to get some other opinions before
> disclosing what it is.
>
> John
> Durban
> South Africa
> Alfetta 1.8L turbo  -  now fitted with a Megasquirt MKII EFI controller!
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