[DeTomaso] Amp gauge

[John Taphorn]

Yes, you can use a shunt; however, your gauge will no longer be 
accurately reading the quantity of charge/discharge without 
recalibration.  It is about as useful as an idiot light at that point.  
Idiot light on, you are discharging, idiot light off you are charging.  
I haven't heard of anyone using a shunt recalibrating their amp gauge.

As I see it.  The real challenge to the amp gauge is connecting the 
larger gauge wire or running additional wiring to it's backside as 
owners ramp up the potential amperage output of their new high output 
alternators to accommodate the higher draw of additional accessories.  I 
have found it extremely difficult to get larger gauge wires safely 
connected to the amp guage's limited real estate on the backside.

Frankly, I would prefer an accurate amp gauge; However, I run a 
voltmeter for the aforementioned limitations.

JT

On 5/19/2012 8:42 AM, shawkins777 at comcast.net wrote:
> I fall into the ammeter more usefull information side, you can limit the current through the dash with a properly sized shunt/gauge.
>
> Steve
>
>
> ----- Original Message -----
>
> From: "Kirby Schrader"<kirby.schrader at gmail.com>
> To: MikeLDrew at aol.com
> Cc: guson at home.se, detomaso at realbig.com, "mikael hass"<mikael_hass at mail.tele.dk>
> Sent: Friday, May 18, 2012 2:25:54 PM
> Subject: Re: [DeTomaso] Amp gauge
>
> Gee, Mike,
>
> I knew how an ammeter worked before you were even born! No need to tell me.
> :-)
> The GT40 _was_ wired wrong and Superformance sent out a wiring 'fix'.
>
> If you want both, by all means do so!
> There has been many a thread on this forum since it started back in
> the mid-90's.
>
> Up to you what you use. I used to be a 'dyed in the wool' ammeter fan.
> I have converted to voltmeters.
>
> Kirby
>
> On Fri, May 18, 2012 at 12:45 PM,<MikeLDrew at aol.com>  wrote:
>> In a message dated 5/18/12 9 41 35, kirby.schrader at gmail.com writes:
>>
>>
>>
>> I disagree and can not at all see how this approach is valuable...
>> That's the way my GT40 came 'incorrectly' wired.
>> As you turned things on (fans came on, A/C compressor, etc. etc.),
>> the ammeter kept climbing as it measured all the loads. Do you really
>> care?
>> I suppose for bragging rights. Look at me!!!! 83 amps!!! Woohoo!
>>
>>
>> That's not how an ammeter is designed to work, and as you said, your car was
>> wired *incorrectly*.
>>
>> If the car is shut off and you start adding loads (turning on lights, fans
>> etc.) then the ammeter registers in the negative, not positive.  When the
>> car is turned on and the alternator is charging, ideally the charge should
>> be slightly higher than the load, so that the gauge indicates slightly
>> positive.  When you first start the car, if your battery is weak, it will be
>> drained quite a bit, so the ammeter will reflect a high state of charge for
>> a minute or two as the charging system rapidly returns the battery to a
>> fully charged state, and then it will come down to show a slight charge
>> (ideally).  If your idle speed is too low, you might show a slight discharge
>> at idle with all your components (lights/fans etc.) running.
>>
>> Sounds like your car had both the supply AND the loads wired on the same
>> side of the ammeter?  That would deliver crazy readings for sure.
>>
>> My point is that it's senseless to take high-load components and wire them
>> outside of the ammeter so that the ammeter never registers their draw when
>> running.  It's like partitioning your fuel tank so that the fuel gauge only
>> registers part of the fuel you have on board.  Doing so guarantees that
>> you'd never know exactly how much fuel you have.  What would the point of
>> that be?
>>
>> An ammeter will instantly indicate a charging system failure because the
>> needle will displace into the negative side, which is easily apparent.  A
>> voltmeter is much more subtle; it will show 12.5 or 13 volts when all is
>> good, and will ALSO show 12.5 or 13 volts if your alternator fell out of the
>> car, because it's just showing the state of charge of the battery.
>>
>> The common fallacy is that the voltmeter tells you about your alternator.
>> It doesn't tell you JACK about your alternator, it only tells you about the
>> state of your battery.  An AMMETER is the only gauge that tells you about
>> your alternator, because it instantly informs you as to whether it is
>> charging the battery, or if the battery is being discharged.
>>
>> Over time, if your alternator clatters onto the roadway, your voltmeter will
>> drift imperceptibly lower as the battery drains, but at a glance it will
>> still look healthy.  When it gets to 11.5 volts or whatever, you'll sputter
>> to a stop with a 'dead' battery.
>>
>> It would be ideal to have both a voltmeter and an ammeter, but given the
>> choice I'd take an ammeter any time.
>>
>> Mike
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