amp gauge/ one wire altenator

[Darren MagooGardner]

when you go to a one wire modern alternator does the nos amp gauge read true?

[VetteVet]

Originally Posted by Darren MagooGardner

when you go to a one wire modern alternator does the nos amp gauge read true?

In order to answer that question I need to explain how the Battery gauge works.
The gauge is an external shunt meter and it measures the voltage differential between the state of charge of the battery and the output voltage of the alternator. In order to do that it must have a shunt between the alternator and the battery. The shunt is nothing more than a length of wire from the battery to the junction of the alternator and the voltage regulator voltage sensing wire and the cab feed wire from the junction.

The pickup lead wires for the battery gauge are at the ends of the shunt. Both wires are positive but they will measure the difference between the battery voltage and the alternator output voltage. If the alternator voltage is higher, then the gauge reads plus, or charge, and if the battery voltage is higher the gauge reads negative or discharge.

Now for the answer to your question. Most of the time the one-wire alternators will be wired in with the output wire ran straight to the battery plus, or to the fusible link terminal on the right passenger fender. This eliminates the shunt and the battery gauge is not able to see any differential between the alternator and the battery and it WILL NOT WORK.

If it is wired exactly like the factory did the stock alternator and as I described, then it will work, providing the gauge, the fuses, and the ammeter wiring is good.

Here is a diagram of the stock factory wiring and in the bottom center is the junction of the battery,alternator, the regulator sensing wire and the shunt and the cab feed wire. The shunt is pointed out by the arrow and is the 12 gauge red wire on the left side of the diagram. It runs over the top of the radiator in the truck harness.




Here is a real time picture of the junction on my 67 harness.

[502ms]

Originally Posted by VetteVet

Now for the answer to your question. Most of the time the one-wire alternators will be wired in with the output wire ran straight to the battery plus, or to the fusible link terminal on the right passenger fender. This eliminates the shunt and the battery gauge is not able to see any differential between the alternator and the battery and it WILL NOT WORK.

If it is wired exactly like the factory did the stock alternator and as I described, then it will work, providing the gauge, the fuses, and the ammeter wiring is good.

Here is a diagram of the stock factory wiring and in the bottom center is the junction of the battery,alternator, the regulator sensing wire and the shunt and the cab feed wire. The shunt is pointed out by the arrow and is the 12 gauge red wire on the left side of the diagram. It runs over the top of the radiator in the truck harness.


Here is a real time picture of the junction on my 67 harness.

Attachment 993907

Great detailed explanation!

My question is about your actual circuit above...at that juncture, what do you have in place to prevent arcing/shorting against the frame or metal in the engine bay? I'd recommend butt splicing those ends to prevent future problems...just a thought. I just completely rewired my entire truck, front to rear, in March. So, I'm protective of things, knowing what it takes to fix it
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[VetteVet]

Originally Posted by 502ms

Great detailed explanation!

My question is about your actual circuit above...at that juncture, what do you have in place to prevent arcing/shorting against the frame or metal in the engine bay? I'd recommend butt splicing those ends to prevent future problems...just a thought. I just completely rewired my entire truck, front to rear, in March. So, I'm protective of things, knowing what it takes to fix it
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Thank you for your comment Leon and don't worry about the open junction, I was opening the harness to re wire the connections and it no longer exists. I thought taking a picture would be great to show how the wires are joined.
I have eliminated that junction and am using a terminal board to make all the connections.

Darren-- Here is the correct way to wire the internal regulated alternator when the external VR is eliminated. If you use a one-wire alternator then the two small wires will be eliminated.

[Darren MagooGardner]

WOW.. It will take me a few days to figure all that out. I eliminated all the components of my old regulator. I may just stick with my under dash gauge. thanks for the info.