The13Bats

So I am curious what did you do with the wires going to the ammeter after you installed the volt meter,

Sacred Steel

I switched to a volt meter and I really did nothing with the ammeter wires except tie them up out of the way.

The13Bats

I understand the system has a shunt but didnt know for sure if it's cool to forget the ammeter wires when we swap to voltmeter,

I love wiring and redoing most of the wiring on my 69 to a better more modern idea,

mrvette

Clip /tie them off separately, and run a wire from SWITCHED hot/ ORANGE off the fuse block.....of course ground to the negative VM post, and call it a day.....

zwede

No need to go to the fuse block. Just tie into the switched power to the temp gauge.

The13Bats

I know the basics

I started rewiring things at about 14-15 and by 20 did it really well...

I was more curious about the factory ammeter wiring with the shunt

7T1vette

You only need to use ONE of the two ammeter leads to hook to the voltmeter. BOTH ammeter leads have 12 vdc on them (one has a few millivolts more than the other, but relative to your voltmeter, that means nothing). The only other connection is a ground lead (which the ammeter does not need).

zwede

Nope. The ammeter lead is always hot. You want the voltmeter to turn on and off with the ignition. The ammeter leads are not used for anything after converting to a voltmeter. Tape them off or remove them, your choice.

7T1vette

Yep. You are correct. Either ammeter lead is 'hot', but the voltmeter should have "switched" power going to it.

The13Bats

This was where I wanted to go, where do those ammeter leads go, does anything else tap into those wires

C3Hawk

On a different note, I would love to switch the ammeter in my '75 to a voltmeter, but haven't been able to find a voltmeter with the old style face and red needle. Anybody make this? Thanks.
(I can start a separate thread for this question if that would be more forum correct)

Swiftrider08

I have the same question for my '76. Use volt gauge from '74 and earlier or '78 and later?

7T1vette

The ammeter leads tap into two spots on the main power line running through the engine compartment. Yes, two spots on the SAME run of wire. The length of wire between those connections (about 18" or so) provides a natural 'shunt' resistor. Even wire has resistance, so that run of wire is used to create a very small (millivolts) voltage drop from one lead to the other. The ammeter (really a galvanometer, calibrated in amps) measures that voltage drop and displays it as amps.

Very little voltage is measured by the ammeter; and VERY small current is passed through it. It only "displays" amps, while it is measuring the millivolt drop across an 18" run of wire.

The connections for those leads are wrapped up inside the main harness bundle; you would have to unwrap it to find the points of connection for those ammeter leads.

jnb5101

I can't understand why owners want to change to a voltmeter. An ammeter is a better indicator of the electrical system than is a voltmeter. A voltmeter only displays one bit of information. An ammeter indicates the condition of the entire charging system. A while back there was a post about a race prepared corvette. If you look closely at the pics of the instrument panel, there is an ammeter, not a voltmeter. The professionals that built this car could have gone either way on the meter. They chose amps!

Big2Bird

Simplicity. With a volt meter, if it's at 14 volts or so, everything is good.
If it drops, something is wrong."Go or no go."

An ammeter will tell you the flow of current, and if you understand it, it will tell you the same thing, only with added information, that frankly, is useless to the average guy.
With an ammeter, if something shows "out of normal range," it still does not tell you what, just something is wrong. A voltmeter does that as well.

The arguments will begin now, but this is a simply as I can state it for the average guy.

'75

I prefer the volt meter and changed to it, I understand the info from both, turn the key on and get a reading from the volt meter, no useful info from the ammeter at that point.

flyeri

Not and argument here Big2Bird. A voltmeter will tell you the voltage present on the electrical system. Period. Not necessarily the condition of the battery or alternator. There are conditions such as a weak battery that shows 12 volts or so unloaded and a good alternator that all will look ok with a voltmeter. An ammeter will indicate a higher charge rate or longer charge time to bring the battery back up after start. You won't see that with a voltmeter. If the alternator is putting out 16 volts you won't know that with a ammeter. Only the voltmeter will tell you that.

The correct answer is that both have a place and give you good information and to get a complete picture of your electrical system health you need both. Most people today have no clue what an ammeter is telling them so voltmeters now are common.

74modified

Here is what has not been said - When you change to a higher output alternator (like OP is doing) the ammeter is not going to be correct. My alternator puts out more than three times what the original did. And with new higher gauge wiring parallel to the old wiring, the 40 amp meter was near useless.

694speed350

and have never understood why anyone would want to change from the amp meter. really a volt meter doesn't tell you anything except you have at least 12.5-13.5 volts so the car will start. seems redundant to me.

694speed350

change the shunt resistor problem solved.