Paul L

If I were to convert my current ammeter (1974) to a later C3 voltmeter, is it a simple matter of running a (+) wire from the meter to the (+) post on the alternator through the firewall via a 16-gauge (or larger) wire and the (-) to a dash/frame ground?

Strangely, I discovered last week that my ammeter never moves from "0", slightly on the (+) side. It has been that way for years. I thought it was normal but I guess not. Someone at a recent show made that comment. Live and learn! I do not have other electrical problems. But I do not wish to introduce any. I do have a new ammeter on order but can return that for a voltmeter. Or should I just drive free of electrical problems.

74modified

You already have a +12v going to the ammeter, so you would just need a ground. But - I would rather have a switched + supply instead of a always live wire. I would rather take one from the fuse box.

Paul L

So IGN?

jyounane

Hi Paul, The voltmeter is high impedance device and a light gauge wire will be fine. In my 69, I connected the (+) voltmeter post to the ignition circuit on the instrument cluster (pink) and the (-) post to ground at the cluster. While the voltage measured might be slightly lower than that at the alternator terminal, it is close enough for my purposes and doesn't require running any additional wires.


Joe

'75

I converted my 75 to a volt meter and just borrowed power from the gauges power wire.

toobroketoretire

The wire that "feeds" your amp gauge connects to a 10-gauge wire right behind your distributor. Unwrap the harness and you'll find a very fine wire that has come undone from the larger 10-gauge wire (that I assume comes from the horn relay. My amp gauge didn't work either and then one day when I was unwrapping the harness behind my distributor I ran across a small single-strand wire that appeared to have been connected to a large 10-gauge wire (hmm). I re-connected it and VIOLA my amp gauge started working and has worked ever since. Try that before swapping gauges.

Paul L

I suppose my real first step is to find out why the ammeter went bad. And go from there. But the voltmeter seems like an easy replacement. The ammeter not so with a shunt/resistor necessary. And now I learn from the ZIP site that a shunt/resistor may not be necessary with modern replacements. I am thoroughly confused. I do want an instrument that shows charging status and I thought the voltmeter was the easy route.

AzMotorhead

Last week I talked at length to the propieter of MAD Electrical.
http://www.madelectrical.com/
Be prepared to spend some time talking to him (45min is a short conversation) He'll tell you everything you need to know about your electrical system,and the way s to improve it.
Believe me this guy knows his old muscle electrical

Paul L

Assuming that I choose to just replace the existing ammeter here is the new unit, just received. Is that black component on the back the shunt resistor? It is plastic and hardly looks like something that would convey AMP flow. I apologize for my electrical ignorance.

zwede

I have a voltmeter on order for my '71 (neat that they are now available in the '71 color & font). Looking forward to installing it as I always considered the ammeter close to useless.

Paul L

That is always an option for me as well. Just thought I would try a replacement ammeter first.

Good to see that you are still on the Forum! You know, 15 years is a long time.

Paul L

I think you are on to something. I had a look and the fusible link in that area is kaput. I can replace that link (solder in) and see what happens. I have 12- and 14-gauge links in the basement. It still begs the question: why did it burn out in the first place? We shall see....

stevelischynsky

Paul
Check this thread:
https://www.corvetteforum.com/forums...amp-gauge.html

There is instructions on how to test your original ammeter using a used battery. But hold the battery connected for only a second to see if the needle moves.

Personally, I would leave the ammeter in place and get a digital voltmeter and plug it into the cigarette lighter.

Despite what others say, the only way to really know what your electricals are doing is to have both and ammeter and a voltmeter. I added a voltmeter on my 73 for decades as an add on meter(digitals weren't invented yet).

example:
If your voltmeter is high and your ammeter is showing a charge, your regulator is probably shot.

If your voltmeter is normal and your ammeter is high, your battery is probably shot.

If your voltmeter is low and your ammeter shows discharge, your alternator may be shot or you have a bad short somewhere.

If your voltmeter is normal and your ammeter shows discharge, you probably have a short somewhere or just have your $5000 stereo turned on and too loud.

The corvette ammeter is really a voltmeter that reads the voltage drop across a known resistance wire that is in parallel with the charging wire. You might have an open in this resistance wire so you will be charging normally but your gauge doesn't work. It's probably a simple fix without buying another ammeter.

Steve L
73 coupe since new
Capital Corvette Club

Paul L

Thanks Steve. Did we meet at Morrisburg or Merrickville? My memory is failing me.

At this point I am left with the two stub (black ****) ends of the fusible link. And I don't know what their purpose is. But their wires are isolated now so no shorts will occur. I have given up for today as tomorrow I have to attend a funeral for a long-time family and dear friend who suffered from dementia for many years. It is so sad to see the mind go and the body persist. But he has now found peace.

I will consider the voltmeter option again and perhaps return the new ammeter for an exchange.

7T1vette

If your battery is in good shape and the car's engine fires quickly, an ammeter will not show much movement...and it shouldn't. If you want to test your ammeter, all you have to do is turn the ignition to ON (not to START), then turn on your headlamps and see what the ammeter reads. It should show about 5-10 amp discharge. Now, turn on the high beams. The meter should show about 15 amp discharge.

If it shows those discharges, the meter and wiring are probably fine. If the meter moves, but not nearly the correct amount, your meter is probably fine...but it is not wired into the harness correctly.

If there is NO movement during this test, your ammeter has failed.

P.S. There is very little current that is passed THRU the ammeter. It really measures the small voltage drop across a lenth of main power wiring in the harness. The scaling on the dial just allows you to read AMPS.

Paul L

I have done all those tests. The ammeter and the fusible link are finished. I am not going to fool with that wiring. The trashed fusible link ends behind the wiper motor are now sealed with black GOOP. I am going with a 1977 voltmeter: (+) to switched 12V source and (-) to dash ground. Simple installation.

The car still runs extremely well. No electrical problems. I am not going to fool about with ammeter wiring and spoil my summer.

learje

i did the swap this spring...plenty of switched 12v right there on the gauge cluster. only thing i dont like is the new gauge is a bit brighter, not sun faded like the other originals, but only i notice it.

easy fix

7T1vette

Sorry I tried to help. I thought you were the one who had the new ammeter and was trying to decide what to do.

Paul L

Your help WAS appreciated. I am the one who can't decide on a ammeter or voltmeter. I pretty well have made up my mind now.

carriljc

You probably want to check your fusible link sections of wiring anyway to ensure they are not about to make contact with something metallic .... below is where the fusible links were located for my 68. Yours may be different and it's easy enough to check.

https://www.corvetteforum.com/forums...locations.html