How ground is ground?

On Sun, 28 Nov 2004 20:45:04 GMT, "Thomas G. Marshall"
. com> wrote:

>
>1999 / Honda CR-V
>
>At the top of the fuse block inside the car there are a bunch of options
>connectors.
>
>Some of you have seen my prior postings concerning turning the cig. lighter
>to "always on".
>
>The question is this:
>
>I know which of these is powered by the battery, always on.

If you find a wire or connection that is always on be careful that
there is not a fuse or relay contact ahead of it. A fuse or relay
contact will Ohm out at 0 Ohms.
>
>But for ground: If I discover one of these options connectors to be 0 Ohms
>resistance (impedance?) from it to the chassis, can I assume that there is
>nothing else "on it" and that it is OK to use as the ground for the cig.
>lighter?
>
>I want to avoid an ugly wire going to a chassis bolt.

I looked at my '01 Honda and looked for a ground point. There were 4
black wires on the screw. I suggest you buy a small package of black
wire at Radio Shack, or wherever, install a crimp connector on the end
of the wire so now you have 5 wires at the ground point and it looks
factory.

>
>Is it possible that there is some signal ground that is different that
>chassis ground that will hurt something else on its circuit once the cig.
>lighter is used?

No! But do make sure the loads are wired in parallel.

When I am designing the Electrical Facilities for a building with GFI
Breakers, I worry about multiground paths but on a car, I wouldn't
worry about it.

Wire size, use #16 or #18, lower number is larger.

Modern cars are full of Integrated Circuits, Computers,etc. so be
carefull. Replacing one could cost big bucks.


If you are going to do a good job, use crimp connectors at the end of
the wire. never twist two wires together and never twist a wire around
a screw.

"Thomas G. Marshall" . com>
wrote in message news:%1vqd.2662$%R1.1265@trndny03...
>
> What I find confusing about these answers of your's and Clarence's is that
> the options connectors are designed for additional equipment to be
> attached.
> At the far left there is a 3 blade connector socket on the options
> connector
> block, which seems to have the center be power and the other two are
> ground.
> Presumably for something known device that needs both power and ground.
> Perhaps one of the blades is ignition, to complete the triad: [always
> on]power, ignition, ground.
>
> The other problem I have is how can that ground connection actually be
> something like the rear window defroster. Wouldn't I be measuring the
> ohms
> as /resistance/ and isn't a heating coil like that designed around the
> heat
> produced by resistance, as in a toaster? I guess I'm not sure I
> understand
> how that would be 0.
>
> But I trust you all----it's the point of me asking the question in the
> first
> place. I'd like to know what that 3 blade connector thing is for if not
> to
> supply a usage ground (with power) to something. It looks like a
> dedicated
> thing.

Sometimes circuits "rest at ground" and "go hot" when activated.

Randolph coughed up:

....[rip]...



> Are you relocating the power outlet, and is that the reason you can't
> use the existing ground for it?


Just a quick question about this question of yours.

Even if I do manage to open up this @#$%ing dashboard and reuse the in-dash
cig. lighter, didn't we decide that using the ground wire to it was a bad
idea?

Isn't it possible that because there is something else on that circuit, that
there might be something that just doesn't like having current flow through
it with the ignition off (for example, when my charger is plugged in
overnight).




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"Thomas G. Marshall" wrote:
>
> Randolph coughed up:
>
> ...[rip]...
>
> > Are you relocating the power outlet, and is that the reason you can't
> > use the existing ground for it?
>
> Just a quick question about this question of yours.
>
> Even if I do manage to open up this @#$%ing dashboard and reuse the in-dash
> cig. lighter, didn't we decide that using the ground wire to it was a bad
> idea?
>
> Isn't it possible that because there is something else on that circuit, that
> there might be something that just doesn't like having current flow through
> it with the ignition off (for example, when my charger is plugged in
> overnight).

Not a problem, the lighter socket ground is a confirmed ground. Current
in this ground lead will not flow *through* anything else in the
circuit. If you are pulling high currents from the lighter socket, there
will be some voltage drop along the ground lead. Other devices using the
same ground wire will have their ground potential elevated ever so
slightly, but this is of no consequence. Also, the wiring to the lighter
socket is designed to handle large currents. Odds are the ground lead to
the lighter socket is shared only with the ash tray light.