battery gauge??

[bdydrp97s10]

i need to know how to wire the battery gauge on a 68.. i would assume the stock gauge just gets a positive on one teminal and a negative on the other.

am i right??

[Anthony Fremont]

No, probably not. If the stock guage is an amp meter, then it is wired in series with the feed from the battery (but after the starter since it draws incredible amount of current) to the rest of the electrical system. Amp meters are kinda dangerous, so I recommend not hooking it up, but instead replace it with a volt meter. A volt meter wires the way you planned and doesn't present a fire hazard.

[bdydrp97s10]

well if they suck that bad and their dnagerous ill will take your advice and not hook it up..

anybody else have any input

[Longhorn Man]

STOCK amp guages are not dangerouse at all.
The vehicle's power does not all go through a stock one like a cheap aftermarket one. It picks up a reading on one side of the harness, and then picks up a reading on the other side, and the difference is shown on the guage. A large difference in a charge state will show many amps on the positive side, the oposite for a large difference in a discharge state.

[72lb4x4]

I tend to doubt that the stock battery gauge in these trucks is an ammeter at all since it uses the PCB which can't take any significant current. It also doesn't claim to be an ammeter.

Its probably a voltmeter with its needle set in the center. Then as LM says, it gets 2 voltage readings, from different spots. They aren't referenced to ground so the needle swings left or right depending on which point's voltage is higher or lower, giving an indication of battery charge, or discharge.

Thus we get the advantages of an ammeter without the dangers.

Chrysler products in the 60's I think used an ammeter and they tend to cook... I think I read that on the Mad electric site.

[Anthony Fremont]

Originally Posted by 72lb4x4

.....Its probably a voltmeter with its needle set in the center. Then as LM says, it gets 2 voltage readings, from different spots. They aren't referenced to ground so the needle swings left or right depending on which point's voltage is higher or lower, giving an indication of battery charge, or discharge.

That would certainly be a much safer way to do it. There were quite a few older vehicles with the dangerous style gauge in them, including Ford pickups from the 60's. Personally, I'm a fan of ordinary volt meters; much safer and more informative.

[LONGHAIR]

Its probably a voltmeter with its needle set in the center. Then as LM says, it gets 2 voltage readings, from different spots. They aren't referenced to ground so the needle swings left or right depending on which point's voltage is higher or lower, giving an indication of battery charge, or discharge

A voltmeter shows the "amount" of voltage...just like a gas guage. It gives no indication of flow.
This is a "zero-center ammeter"
An ammeter indicates not only the flow of electricity, but the direction of that flow. "Positive", showing that the Alternator is charging (putting power into the battery)....or "Negative" meaning that the current draw is more than the alternator can keep up with.

[neonlarry]

Actually all ampmeters are voltmeters across a bridge circuit. You just can't flow that many amps thru the tiny wires on one of those small meters. The voltmeter just happens to measure +or- from 0 which is the center.
Our particular ampmeter is like longhornman said across a very large bridge circuit.

[Anthony Fremont]

Originally Posted by LONGHAIR

A voltmeter shows the "amount" of voltage...just like a gas guage. It gives no indication of flow.
This is a "zero-center ammeter"
An ammeter indicates not only the flow of electricity, but the direction of that flow. "Positive", showing that the Alternator is charging (putting power into the battery)....or "Negative" meaning that the current draw is more than the alternator can keep up with.

Actually a voltmeter can be used to indicate the amount of current flow when placed across a resistance, such as that in the wiring harness between the battery and the alternator/voltage regulator. If the battery is discharging, the voltage will be slightly higher at the battery post than at the alternator/vr. If the alternator is charging the battery, the reverse will be true. It's an Ohm's Law thing.

[72lb4x4]

A voltmeter indicates a difference in potential between two points. It doesn't have to be referenced to ground.

Since there can be no significant current flowing through the "battery gauge" it follows that this is possibly/probably a special application of a voltmeter.

Take an old style DC voltmeter, connect it backwards, and the needle will go backwards, or to the left. Make a voltmeter with the needle in the center, and apply 2 voltages to it. Now you get an indication of the difference in potential of the 2 voltages. This is shown by the direction the needle moves.

Connected correctly, it will indicate whether or not the battery is being charged or discharged.

"Direction of flow" is meaningless, since there are theories and models that use current flowing from + to - and - to +. All that matters here is charge vs discharge.

A voltmeter used as described can do this as I explained. A little creative thinking is all that's needed.

Anybody have a gauge from one of these trucks and an Ohmmeter handy?

[MattyBs71]

Originally Posted by bdydrp97s10

i need to know how to wire the battery gauge on a 68.. i would assume the stock gauge just gets a positive on one teminal and a negative on the other.

am i right??

You are not right in your thinking above. I can help you as I just completed this task on my truck a '71. I need to know a bit of background info though.

Did your truck originally come with gauges or idiot lights (3 hole cluster)?

I need to know this as this will determine if you have to move around some pins in the dash cluster harness, and also run wires with inline fuse to the battery and voltage regulator. Let me know those things and we can go from there.