Grounded circuit troubleshooting

I have a 71 Opel GT with a dead short in the instrument panel lunination
circuit. What is the best way to isolate the ground as it seems that
everything is tied together into one big mess. Are there any free
internet sites that explain basic ammeter use and trouble shooting of
grounded circuits. My experiance with meter use is none and would like to
learn more in this area.

Thanks

opps, should have also mentioned a test buzzer. same as the test light but
it makes a sound which is sometimes better when working in places where you
can't see.

William R. Watt ) writes:
> A test light can be used. It's simpler and cheaper, just a light bulb with
> two wires comming from it. Touch the wires to two pices of metal and if a
> current is flowing it will illuminate the bulb.
>
> "dontlookback" ) writes:
>> I have a 71 Opel GT with a dead short in the instrument panel lunination
>> circuit. What is the best way to isolate the ground as it seems that
>> everything is tied together into one big mess. Are there any free
>> internet sites that explain basic ammeter use and trouble shooting of
>> grounded circuits. My experiance with meter use is none and would like to
>> learn more in this area.
>>
>> Thanks
>>
>
>
> --
> ------------------------------------------------------------------------------
> William R Watt National Capital FreeNet Ottawa's free community network
> homepage: www.ncf.ca/~ag384/top.htm
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On 30 Oct 2005 22:48:19 GMT, (William R.
Watt) wrote:

>
>A test light can be used. It's simpler and cheaper, just a light bulb with
>two wires comming from it. Touch the wires to two pices of metal and if a
>current is flowing it will illuminate the bulb.

If there is a voltage differential between the two pieces of metal
touched with the probe wires, then a voltage differential will be
displayed.
Example:
1 wire is at 100 volts
the other wire is at 300 volts

what do you think you will read between these wires if these wires are
in an open circuit?

The answer is:

between eachother, 200 volts
between100 volts and earth ground or neutral safety bus, 100 volts
between 300 volts and earth ground or neutral safety bus, 300 volts

This has nothing at all to do with current. There can be zero current
flowing in the wires, and you will still measure this voltage.

Amperes is the unit of measurement for current.

What if -both- wires are alive with 300 volts? What will you read?

ZERO VOLTS if you just put your probes on the two wires, each carrying
300 volts!

IOW, if you don't know what you're doing, DON'T DO IT.

Lg


>
>"dontlookback" ) writes:
>> I have a 71 Opel GT with a dead short in the instrument panel lunination
>> circuit. What is the best way to isolate the ground as it seems that
>> everything is tied together into one big mess. Are there any free
>> internet sites that explain basic ammeter use and trouble shooting of
>> grounded circuits. My experiance with meter use is none and would like to
>> learn more in this area.
>>
>> Thanks
>>

Ageed, for sure!!
"Lawrence_Glickman" > wrote in message
...
> On 30 Oct 2005 22:48:19 GMT, (William R.
> Watt) wrote:
>
>>
>>A test light can be used. It's simpler and cheaper, just a light bulb with
>>two wires comming from it. Touch the wires to two pices of metal and if a
>>current is flowing it will illuminate the bulb.
>
> If there is a voltage differential between the two pieces of metal
> touched with the probe wires, then a voltage differential will be
> displayed.
> Example:
> 1 wire is at 100 volts
> the other wire is at 300 volts
>
> what do you think you will read between these wires if these wires are
> in an open circuit?
>
> The answer is:
>
> between eachother, 200 volts
> between100 volts and earth ground or neutral safety bus, 100 volts
> between 300 volts and earth ground or neutral safety bus, 300 volts
>
> This has nothing at all to do with current. There can be zero current
> flowing in the wires, and you will still measure this voltage.
>
> Amperes is the unit of measurement for current.
>
> What if -both- wires are alive with 300 volts? What will you read?
>
> ZERO VOLTS if you just put your probes on the two wires, each carrying
> 300 volts!
>
> IOW, if you don't know what you're doing, DON'T DO IT.
>
> Lg
>
>
>>
>>"dontlookback" ) writes:
>>> I have a 71 Opel GT with a dead short in the instrument panel lunination
>>> circuit. What is the best way to isolate the ground as it seems that
>>> everything is tied together into one big mess. Are there any free
>>> internet sites that explain basic ammeter use and trouble shooting of
>>> grounded circuits. My experiance with meter use is none and would like
>>> to
>>> learn more in this area.
>>>
>>> Thanks
>>>
>
>



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Wow.....

Are you two fools for real?

It's an old 12 volt car with a short.....

What's he gonna do, blow a fuse? LOL!

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
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(More Off Road album links at bottom of the view page)

Shep wrote:
>
> Ageed, for sure!!
> "Lawrence_Glickman" > wrote in message
> ...
> > On 30 Oct 2005 22:48:19 GMT, (William R.
> > Watt) wrote:
> >
> >>
> >>A test light can be used. It's simpler and cheaper, just a light bulb with
> >>two wires comming from it. Touch the wires to two pices of metal and if a
> >>current is flowing it will illuminate the bulb.
> >
> > If there is a voltage differential between the two pieces of metal
> > touched with the probe wires, then a voltage differential will be
> > displayed.
> > Example:
> > 1 wire is at 100 volts
> > the other wire is at 300 volts
> >
> > what do you think you will read between these wires if these wires are
> > in an open circuit?
> >
> > The answer is:
> >
> > between eachother, 200 volts
> > between100 volts and earth ground or neutral safety bus, 100 volts
> > between 300 volts and earth ground or neutral safety bus, 300 volts
> >
> > This has nothing at all to do with current. There can be zero current
> > flowing in the wires, and you will still measure this voltage.
> >
> > Amperes is the unit of measurement for current.
> >
> > What if -both- wires are alive with 300 volts? What will you read?
> >
> > ZERO VOLTS if you just put your probes on the two wires, each carrying
> > 300 volts!
> >
> > IOW, if you don't know what you're doing, DON'T DO IT.
> >
> > Lg
> >
> >
> >>
> >>"dontlookback" ) writes:
> >>> I have a 71 Opel GT with a dead short in the instrument panel lunination
> >>> circuit. What is the best way to isolate the ground as it seems that
> >>> everything is tied together into one big mess. Are there any free
> >>> internet sites that explain basic ammeter use and trouble shooting of
> >>> grounded circuits. My experiance with meter use is none and would like
> >>> to
> >>> learn more in this area.
> >>>
> >>> Thanks
> >>>
> >
> >
>
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AC OR DC???????

Lawrence_Glickman wrote:
> On 30 Oct 2005 22:48:19 GMT, (William R.
> Watt) wrote:
>
>
>>A test light can be used. It's simpler and cheaper, just a light bulb with
>>two wires comming from it. Touch the wires to two pices of metal and if a
>>current is flowing it will illuminate the bulb.
>
>
> If there is a voltage differential between the two pieces of metal
> touched with the probe wires, then a voltage differential will be
> displayed.
> Example:
> 1 wire is at 100 volts
> the other wire is at 300 volts
>
> what do you think you will read between these wires if these wires are
> in an open circuit?
>
> The answer is:
>
> between eachother, 200 volts
> between100 volts and earth ground or neutral safety bus, 100 volts
> between 300 volts and earth ground or neutral safety bus, 300 volts
>
> This has nothing at all to do with current. There can be zero current
> flowing in the wires, and you will still measure this voltage.
>
> Amperes is the unit of measurement for current.
>
> What if -both- wires are alive with 300 volts? What will you read?
>
> ZERO VOLTS if you just put your probes on the two wires, each carrying
> 300 volts!
>
> IOW, if you don't know what you're doing, DON'T DO IT.
>
> Lg
>
>
>
>>"dontlookback" ) writes:
>>
>>>I have a 71 Opel GT with a dead short in the instrument panel lunination
>>>circuit. What is the best way to isolate the ground as it seems that
>>>everything is tied together into one big mess. Are there any free
>>>internet sites that explain basic ammeter use and trouble shooting of
>>>grounded circuits. My experiance with meter use is none and would like to
>>>learn more in this area.
>>>
>>>Thanks
>>>
>
>

Mike Romain > wrote:
>Wow.....
>
>Are you two fools for real?
>
>It's an old 12 volt car with a short.....
>
>What's he gonna do, blow a fuse? LOL!

What he can do is melt a wire, or an entire wiring harness, allowing a lot
of current to flow through it while trying to find a short.

At least, that's what I did when I was eighteen and stupid. (It did turn
out, though, that the insulation was all turning to goo and I had to rewire
the whole car anyway.)
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 30 Oct 2005 19:29:12 -0500, (Scott Dorsey) wrote:

>Mike Romain > wrote:
>>Wow.....
>>
>>Are you two fools for real?
>>
>>It's an old 12 volt car with a short.....
>>
>>What's he gonna do, blow a fuse? LOL!

================================================== =====
>What he can do is melt a wire, or an entire wiring harness, allowing a lot
>of current to flow through it while trying to find a short.

There's your answer *Wise Guy*

Lg
================================================== =====

>At least, that's what I did when I was eighteen and stupid. (It did turn
>out, though, that the insulation was all turning to goo and I had to rewire
>the whole car anyway.)
>--scott

On Mon, 31 Oct 2005 00:28:49 GMT, KENG > wrote:

>AC OR DC???????

Bob told me you're both.


>Lawrence_Glickman wrote:
>> On 30 Oct 2005 22:48:19 GMT, (William R.
>> Watt) wrote:
>>
>>
>>>A test light can be used. It's simpler and cheaper, just a light bulb with
>>>two wires comming from it. Touch the wires to two pices of metal and if a
>>>current is flowing it will illuminate the bulb.
>>
>>
>> If there is a voltage differential between the two pieces of metal
>> touched with the probe wires, then a voltage differential will be
>> displayed.
>> Example:
>> 1 wire is at 100 volts
>> the other wire is at 300 volts
>>
>> what do you think you will read between these wires if these wires are
>> in an open circuit?
>>
>> The answer is:
>>
>> between eachother, 200 volts
>> between100 volts and earth ground or neutral safety bus, 100 volts
>> between 300 volts and earth ground or neutral safety bus, 300 volts
>>
>> This has nothing at all to do with current. There can be zero current
>> flowing in the wires, and you will still measure this voltage.
>>
>> Amperes is the unit of measurement for current.
>>
>> What if -both- wires are alive with 300 volts? What will you read?
>>
>> ZERO VOLTS if you just put your probes on the two wires, each carrying
>> 300 volts!
>>
>> IOW, if you don't know what you're doing, DON'T DO IT.
>>
>> Lg
>>
>>
>>
>>>"dontlookback" ) writes:
>>>
>>>>I have a 71 Opel GT with a dead short in the instrument panel lunination
>>>>circuit. What is the best way to isolate the ground as it seems that
>>>>everything is tied together into one big mess. Are there any free
>>>>internet sites that explain basic ammeter use and trouble shooting of
>>>>grounded circuits. My experiance with meter use is none and would like to
>>>>learn more in this area.
>>>>
>>>>Thanks
>>>>
>>
>>

"dontlookback" wrote

> I have a 71 Opel GT with a dead short in the instrument panel lunination
> circuit. What is the best way to isolate the ground as it seems that
> everything is tied together into one big mess. Are there any free
> internet sites that explain basic ammeter use and trouble shooting of
> grounded circuits. My experiance with meter use is none and would like to
> learn more in this area.

Dead short meaning you blow the fuse every time you turn on the lights?

As others have suggested, use a test light or buzzer, but wire it to *replace*
the fuse that keeps blowing. That will keep the current down to a reasonable
level, as it has to go through the test light before the short to ground.

Remove every bulb that the circuit runs (I've seen bulbs where the filament
supports inside have fused, causing a short), and if the test light is still lit,
move on to the wiring, looking for frayed connections, insulation that's rubbed
off where it goes through bulkheads, etc.