How to still use dash amp guage

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olddman

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Would like to add a single charging circuit to my 1965 Dodge Dart GT that will route alternator current directly to the battery. Will be using a dual field post alternator for a 1970 model Dodge. Alternator is 65 amps. Will run two 8 gauge wires with a fusible link from positive side of battery and secure them to the battery post on the starter relay.
Another wire would run from the field side of the alternator to the battery post on the starter relay.
From what I have read the amp meter in the dash would be useless. How can I do this and still use the amp meter in the dash? Or can someone tell me how to rewire so that I can by-pass the bulkhead connector and still use the dash gauge?
 
You have several choices, some of them not really "easy."

1--You can drill out the bulkhead terminals, or provide alternate entrance points, and run heavier wire into the interior and to the original ammeter. This is actually essentially the way Ma did it for a very long time, known variously as "fleet, taxi," or "police" wiring. This is documented in some service manuals. Of course the original ammeter must be in good shape.

2--Contact Bill Grissom, who used a pair of back--to -- back diodes as a sort of variable shunt out in the engine bay to reduce current through the ammeter circuit

One thread on this:

http://www.forabodiesonly.com/mopar/showthread.php?t=228991

3--Look this thread over and decide if you'd be happy with a voltmeter. There's 3 pages on converting various clusters to a voltmeter in the ammeter "hole."

http://www.forabodiesonly.com/mopar/showthread.php?t=119480&page=2

4--If you are pretty handy, you might be able to convert the old ammeter "hole," in the same manner as a voltmeter above, to what is called an "external shunt" ammeter. All U.S. manufactuers used this, even Mopar in the mid--late '70's at least in the C bodies. This approach uses a "sensitive" meter movement, connected out into the engine bay with light gauge wire, with a "shunt" out in the engine bay.

I say "shunt," because whether GM, Ferd, or Ma, they all actually used the underhood charging line AS THE SHUNT. I was going to try this myself, but have been quite happy with a voltmeter conversion.
 

If you are good with electronics, there are Hall effect current sensors that measure current in proximity to a current carrying conductor. The dash gauge could be freed of the shunt and driven by the Hall current sensor with a few additional components.
 
Hmmmmmmmmmmmmmmmmmmm......................

I "ain't" good enough to do design work with that but I'd bet you are.....................
 
I think you could. There are many companies that make sensors Allegro, Infineon, Melexis ... I like them because the eliminate a shunt and connections after calibration if that is even necessary. Data sheets often have good instructions and sample circuits.

I thought of another way that I used on my electric car. I used a battery cable as the shunt and added resistor and pot to calibrate uA meter as gauge.
 
Thanks for all the ideas. May look into trying the police wiring. Sounds like it may be a simple way to hook up the amp gauge. Will also take a look at the other ideas.
Do you think this is a good thing to do now or should I just leave things alone and consider this change if problems develop later on with the bulkhead connections?
 
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