garretthes

Is it possible to use my original volt gauge on my 59 Chevy truck with my 5.3 engine and factory wiring? If so, how should we wire it? It's the last thing to do in the wiring.

67rsss

iTrader: (4)

Your 59 had a voltmeter? Are you sure it isn't an ammeter? If it is an ammeter, it has two leads to measure the current accross a given stretch of wiring. Hook them back up in the same places. On most 60's GM that would be at the splice and at the distribution block by the battery. If it really is a voltmeter, hook it up either at the splice or at the horn relay. Make sure the other end gets a good ground.

garretthes

Sorry, I meant ammeter. We have done away with the old 59 wiring completely while keeping the original headlight switch. Where would we interface the ammeter in the 2004 factory LS1 harness?

67rsss

iTrader: (4)

It just needs to read accross the feed line from the battery to the distribution location. You could connect one end at the alternator post, and one end on the safe side of the fusible link. I have a drawing of this on my post (down the page a little about a rough draft) about wiring as we used the factory ammeter...

67rsss

iTrader: (4)

Here are a few pics that may help...

G-Body

iTrader: (4)

You should look into the capacity of your ampmeter before you decide to use it. I think that the LSx alternator is capable of putting out 100 amps. If your ampmeter is not capable of handling that it could cause a fire. It is probably unlikely that the alternator would be charging at 100 amps for long enough to cause the ampmeter to overheat and cause a fire, but it is something to consider.

garretthes

Fire + 49 year old Truck = Bad

67rsss

iTrader: (4)

We have not hit a point where ours shows much deflection. Also, he is not running the vehicles full curent through the ammeter like in a Mopar, but only measuring a smaller current based on the voltage drop accross another stretch of wire (the wire between the battery and the splice). The GM ammeter setup (at least from the 60's) is a much safer unit design, and does not measure actual current flow. G-body, think of a parrallel circuit in which one resistance is much greater than the other (lets use 1 ohm for the wire, and 100 ohms for the meter, both are toatlly made up numbers that are convenient to the example). We are going to assume the battery is down to 9VDC and the alternator is at 14.3VDC. Note that the ammeter only measures the charging current to the battery (or the current drain from the battery) it does not measure the output current of the alternator. The total current through the circuit may be great (5.3 Amps in this case). Total resistance is a hair under 1 ohm (.990099 ohm) but for this example we will leave it at 1 ohm. While there is 5.3A flowing through the 1 ohm resistor, there is only 53mA flowing through the 100 ohm resistor. Because the total flow can be found be multiplying the measurement by a factor (100 in this case) we can easily figure out the current without having to pass the full charging system through the ammeter (like a Mopar). Now I don't know for certain that his original gauge from a 59 functions as this way, but I do know that later versions do. Garret, if your original full electrical system ran through your ammeter, you would want to be cautios about using it with a newer charging system with lots of accesories, but if your gauge made a relative measurement (like accross a wire), then go ahead and use it.

G-Body

iTrader: (4)

hmm, I didn`t know that the 60`s GM amp gauges used a current shunt instead of directly measuring the current. That is a much safer design. I wonder how much current it is capable of handling.

Rodder

iTrader: (2)

The stock 1st F-body design taps the battery feed wire at both ends and uses it as a shunt. Not particularly accurate, but it makes the needle move the right directions.

67rsss

iTrader: (4)

It isn't very accurate at all, in fact it doesn't have any kinda of reading other than charge/discharge, but it is safe, easy, and lets you know when you are draining the battery!