I am pretty sure that the original poster meant ammeter. From his
description it wouldn't make sense to have all that heave gauge wire going
to a voltmeter. They are such high impedance that you can hook a voltmeter
up to the battery with very fine gauge wire and have it work fine. I think
most of those cheapie aftermarket voltmeters use 22 gauge to hook up. I
agree with Mark there is no inherent danger from the ammeter as long as it
is in good working order and has good tight clean connections. Many of the
older trucks had little or no fusing at all so every circuit was a
potential problem relying only on the wire burning out before a fire started.
At 07:34 PM 5/3/2002 -0700, you wrote:
>
>Both my Chevy Sub and my GMC NAPCO are 225 miles away at my brother's
house, but I do
>have my Chevy instrument cluster here with me and it has an ammeter
(amps) gauge in the
>dash and not a voltmeter.
>
>Does the GMC have a voltmeter or an ammeter?
>
>Is this the orginal gauge or an aftermarket?
>
>I couldn't quite tell from your description but I assume that it is hooked
up per the
>shop manual.
>
>An ammeter is a voltmeter with a current shunt built into it or on the
back of it. The
>voltmeter measures the voltage drop across the current shunt and the meter
movement
>(needle) is scaled to reflect current thru the shunt. The shunt that is
part of the
>meter is designed to take that kind of current indefinitely.
>
>The Chevy gauge has a built in shunt...ie, you can't modify it easily, but
it could be
>done. I would assume that the GMC unit is similar.
>
>However the main issue is that the approach that you are concerned about
has been normal
>practice for much of the 20th century and has never been considered
dangerous or
>unreasonable. As long as the wires are in good condition and the
terminals are clean
>and tight, you should be fine.
>
>Yes, some vehicles use a voltmeter instead and infer condition of the
charging system
>from the voltage. The ammeter approach directly measures whether you're
charging or
>discharging and by how much. Both approaches are widely used; neither is
considered to
>have a notable safety advantage over the other.
>
>Mark Noakes
>58/56 Chevy Suburban
>58 GMC NAPCO pickup
>59 GMC Suburban
>Knoxville, TN
>
>SurfDudeSC@aol.com wrote
>
>>
>> So I'm rewiring my 57 GMC 1/2 ton and behold.
>>
>> Start solenoid (battery) -- to -- discharge side of voltmeter.
>> Alternator primary -- to -- charge side of voltmeter.
>> Ignition switch (battery terminal) -- to -- charge side of voltmeter.
>>
>> All 10 guage red primary wire with battery amperage running through one
tiny
>> little voltmeter in a steel dash in the cab waiting to short out and fry
>> right before my eyes (or my 15 year old son's, see its his truck I just do
>> all the mechanical work on it).
>>
>> THERE HAS TO BE A BETTER WAY!!! Any advice appreciated to get those amps
>> outside of the cab where they belong. Thanks. David
>>
>> 57 GMC 1/2 ton, original 270 engine.
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
>
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Bill Bailey
57 Chevy 3100
Hagerstown, MD
http://members.tripod.com/~oltruck
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