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Hi All,

So I had a wiring issue with my stock Alternator setup and long story short until I can figure it out I converted to a one wire alternator setup. My 1969 Z car has factory Console gauges but now the Amp gauge is not reading anything.

Is there a way to connect it so that I at least know that they system is working?

Yes it is a real z and yes I kept the original alternator... Someday I amy put it back but for now it's on the shelf.
 

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Single wire systems require the swap to a volt meter. Not saying the amp can't be Gerry-Rigged but don't know how reliable the output would be.


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Why wouldn't a stock ammeter wired in the stock configuration work with a one-wire alternator? There's still current running to and from the battery.
 

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If you happen to have the alternator cable connected to battery positive, connect it to the horn relay bus bar as original instead and it should start reading again.
 

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If you happen to have the alternator cable connected to battery positive, connect it to the horn relay bus bar as original instead and it should start reading again.
Wired as you describe, it should read anyway, just not like you might expect. The current goes from the alternator to the battery post, then through the ammeter shunt to the horn relay. The reading would be on the discharge side all the time.
 

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Wired as you describe, it should read anyway, just not like you might expect. The current goes from the alternator to the battery post, then through the ammeter shunt to the horn relay. The reading would be on the discharge side all the time.
Yep, you're right. So the question becomes "What is meant by not working?"
If reading zero then which little ammeter wire got disconnected?
Or
If never showing charge then where is the alt connected?
 

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Also consider the stock ammeter is a shunted volt meter but it was never intended for the amperage a one wire out puts. You may have blown the resister in the shunt. The reason the factory went to volt meter instead of an ammeter is the cost for an accurate ammeter in the range a one wire puts out. Volt meters are much cheaper and show charging by exceeding the 12.7 volts of a nominal system.

Larger Dave
 

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I can't say it is correct to do this, but I has the same issue with not knowing if my amp meter was working. If you completely disconnect it from the circuit, and you use a 1.5 v battery and touch it to the terminals for a quarter of a second, you should see needle deflection. Don't keep it there long, and you can reverse it to see deflection both directions. Just be quick about it.
 

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Also consider the stock ammeter is a shunted volt meter but it was never intended for the amperage a one wire out puts. You may have blown the resister in the shunt. The reason the factory went to volt meter instead of an ammeter is the cost for an accurate ammeter in the range a one wire puts out. Volt meters are much cheaper and show charging by exceeding the 12.7 volts of a nominal system.

Larger Dave
The ammeter measures the current to and from the battery. When the engine is not running, it measures the draw from the battery. Once the engine is running the current to the battery is that needed to recharge it, then a small trickle current to keep it fully charged. The alternator output capability should not affect this if you wire it in a stock configuration.
 

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You can not run 120 Amps (the average power rating of a one wire alternator) through a 60 Amp ammeter (the size of a lot of old school meters). It will fry it.

The ammeters in the car are shunted, that is they have a resister in series with the load that can sample the current as opposed to metering all of it directly. However they still have an amperage limit. You don't want to let the sacred smoke out of a meter by running more power through it than it was rated for.

Big Dave
 

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You can not run 120 Amps (the average power rating of a one wire alternator) through a 60 Amp ammeter (the size of a lot of old school meters). It will fry it.

The ammeters in the car are shunted, that is they have a resister in series with the load that can sample the current as opposed to metering all of it directly. However they still have an amperage limit. You don't want to let the sacred smoke out of a meter by running more power through it than it was rated for.

Big Dave
Why would you run 120 amps into your battery? Can you name one instance where this is a good idea? You know that the ammeter is in series with the battery charge wire. If I was a GM engineer, I'd use the horn relay as my main power distribution point, put the 120 amps direct from the alternator to the horn relay where it is distributed throughout the electrical system. I would wire the battery to be a load and monitor the current to and from the battery with the ammeter. That way, the ammeter never sees more than the current to and from the battery, not the total output of the alternator, and doesn't depend on the size of the alternator.
 

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The ammeter in a '69 is not in series with the charge wire, it's parallel to it. The charge wire is the shunt and the ammeter is not a true ammeter but really acts more like a transducer and just reads millivolts drop one way or the other. Positive side to horn relay, negative side to battery post or junction block behind the battery. Alt side higher, needle deflects to charging. Battery side higher, needle deflects to discharging. The little wires for it are about 20AWG, one black and one black with white stripe but I do not remember which is which because I've never worked on one of these that the wiring wasn't already hacked.....usually just hook it up and turn the lights on to see which way it swings and then swap the wires at the gauge if it's wrong.
 

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Some of you guys have a gross misconception of alternators, ammeters and electricity. Stock alternators were rated at 31, 37 or 63 amp outputs and were perfectly adequate for all the electrical loads in these old cars and could still charge the battery at the same time. The charge wire from the alternator went to the horn relay terminal which acts as a distribution point for all the electrical current needed by the car. The alternator is connected to the horn relay with a length of 10 gauge wire. That wire is rated at 30Ato 50A depending on the wires temperature ratting and insulation type. A normal 90 degree C rated THHN cable is rated at 30A. The 12 gauge charge wire from the horn relay terminal to the battery is rated at 20A. Putting a 160A alternator in the car and connecting it straight to the battery positive terminal will severely overload that charge wire assuming you had a need to all that current somewhere else in the car (huge stereo system, electric fans hydraulic suspension system, etc) and your asking for a fire in your wiring harness. All of that junk needs to have their own positive power cables run straight off the battery terminal, with their own fuses sized to protect the size of the wire you use to connect the loads to the battery.

That 6 foot length of no. 12 gauge charge wire is the shunt for the ammeter so if you increase its size to carry more current you lower the resistance of the shunt and the gauge becomes less sensitive (effectively the scale of the ammeter increases). The ammeter in these cars is only meant to monitor the current flowing to and from the battery over that charge wire, it does not monitor the output of the alternator, as that is immaterial to the operation of the car. If the battery is charging there is enough current being produced by the alternator and that's all the gauges are meant to do. Be aware of what you are doing when you add large electrical loads to these older cars (or any car) as the wiring systems were never designed to carry any continuous current loads higher than about 15 amps on any one circuit, and no more than 30 over all of the circuits. If you have a need for 160A of current, I'm hoping you made significant wiring modifications to support that load.
 

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Some of you guys have a gross misconception of alternators, ammeters and electricity. Stock alternators were rated at 31, 37 or 63 amp outputs and were perfectly adequate for all the electrical loads in these old cars and could still charge the battery at the same time. The charge wire from the alternator went to the horn relay terminal which acts as a distribution point for all the electrical current needed by the car. The alternator is connected to the horn relay with a length of 10 gauge wire. That wire is rated at 30Ato 50A depending on the wires temperature ratting and insulation type. A normal 90 degree C rated THHN cable is rated at 30A. The 12 gauge charge wire from the horn relay terminal to the battery is rated at 20A. Putting a 160A alternator in the car and connecting it straight to the battery positive terminal will severely overload that charge wire assuming you had a need to all that current somewhere else in the car (huge stereo system, electric fans hydraulic suspension system, etc) and your asking for a fire in your wiring harness. All of that junk needs to have their own positive power cables run straight off the battery terminal, with their own fuses sized to protect the size of the wire you use to connect the loads to the battery.

That 6 foot length of no. 12 gauge charge wire is the shunt for the ammeter so if you increase its size to carry more current you lower the resistance of the shunt and the gauge becomes less sensitive (effectively the scale of the ammeter increases). The ammeter in these cars is only meant to monitor the current flowing to and from the battery over that charge wire, it does not monitor the output of the alternator, as that is immaterial to the operation of the car. If the battery is charging there is enough current being produced by the alternator and that's all the gauges are meant to do. Be aware of what you are doing when you add large electrical loads to these older cars (or any car) as the wiring systems were never designed to carry any continuous current loads higher than about 15 amps on any one circuit, and no more than 30 over all of the circuits. If you have a need for 160A of current, I'm hoping you made significant wiring modifications to support that load.
^^ This!
 
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