jrzvette

A while back the battery in my corvette died. I jump started it and every thing seems fine. However, the ammeter never moved into the positive (+) area. It is either straight uo (at the "0" mark) or if the car is running and the headlights are on it moves slightly into the negative area. I know its possible the gauge is defective, but what exactly should it show?

BB wowbagger

:withstupid:
My Ammeter does the same.. :cheers:

Missileman

The Corvette ammeter is not a precision calibrated unit. It is really more of a voltmeter reading the difference in potential between the alternator and the battery harness. The best thing to do is hook up a voltmeter to the back of the alternator and start the car. Then turn on your accessories one at a time and leave them on until you measure the voltage output with all accessories on. Then look at the ammeter. You can then estimate the voltage output compared to the ammeter needle deflection. This will give you a warm fuzzy on the ammeter calibration.
Some older alternators will not output full voltage until approx. 1000 rpm. So you might have to bump up your idle during the test.

desi

Mine shows slightly above "0" while the car is running. I am assuming "0" means 12 volts. When the car is running, battery being charged, it should be around 14 volts. When I use any accessory, like windows, the voltage drops to negative. The drop is more if both windows are operated at the same time.

isosceles

:iagree:
My meter shows 16 volts when my handheld digital mulitmeter reads 14

norvalwilhelm

An ammeter is hooked in series and current flows through it. It reads the amount of amps being put out by the alternator. How can it read voltage. The battery could be dead and the ammeter could still show a positive reading.
I really prefer a voltmeter and it is hooked in parallel. One wire anywhere there is 12 volts and the other wire to ground. No current flows through it and it tells the overall condition of the charging system and battery. With the motor not running is shows battery voltage and when the motor is running the charging voltage.

bigvette1

The previous post is correct in the function of the ammeter. It is showing the charging o/p of the altenator. It is charging (+) or discharging (-) due to an overload on the capacity of the alterator output, or (0) meaning the charge output has equalized with the battery - or no charge at all - broken.

The best of all worlds is to add a voltmeter and keep the ammeter in the dash as a charge indicator. Get one that reads in increments so you can see the standard o/p of the alternator being 13.8 - 14.2vdc. Outside of these ranges is too little or too much.


[Modified by bigvette1, 1:17 PM 7/29/2003]

LAvetteman

:iagree: Amps = ammeter

73- 454 Monster

Volt meter is the only way of telling if you charging system is operating correctly. Better yet for around $5 at Walmart I bought a battery tester the one you plug in your lighter, rather then pluging in the lighter I cut-off the end and hard wired it and double side tape and stuck it on the side of the cosole blends in real nice, real cool if the led is green you are rocking if the led is amber then the alternator is not putting out enough juice " this usualy happends at idle" If the led is red then you better fix the charging system. This little $5 item is the best upgrade you can do for the money.

Dwayne 76

That sounds like a good idea.

SuperFast80

73- 454 monster:

:troll cough, troll, cough :troll

BB wowbagger

:rofl: :lolg: :lolg:

Alwyn678

:lolg: :withstupid:

Eddie 70

My ammeter does a lot of moving. Hardly ever is it at 0 unless the car is turned off. When I am running it is usually on the plus side. And if after just starting is farther to the plus side. If the fans are on it will drop closer to the midpoint. If idling it will drop to the negative side. I believe my electrical charging system to be in good shape. New battery and the alternator was rebuilt at the same time the engine was rebuilt.

An ammeter shows how much current is flowing in a circuit and is in series with that circuit. A voltmeter shows the voltage of that circuit and is in parallel to the circuit.

mrvette

Norval, as usual is correct in what he says, but he didn't go far enough,
in a stock shark, the amp meter is hooked in series with the feed wire to the regulator sense circuit....and without that meter being jumped you will never get charging current....if you hook up somehting around that meter, you will never get full indications....and they are not a whole lot anyway....

the facts of the matter are...an ampmeter of ANY configuration is nearly useless....a voltmeter is what you need....

GENE

Diode

The perfect world scenario is both a voltmeter and an ammeter (not "ampmeter", sorry folks). The ammeter will indicate instantly if the battery is discharging (meter goes negative) which lets you know that your belt broke or your alternator died. If there isn't much of a load (lights off, blower off, etc.) the battery voltage is going to take a little while to start dropping so you may not notice the change on the volt meter as quickly. Of course though, the volt meter is a better diagnostic aid in terms of regulator / alternator performance. I like the LED volt meter thingy mentioned here. If you want to get REALLY creative, take it all apart and mount the LEDs right in the face of the stock ammeter. Now THAT would look trick. FWIW – as somebody else here said, the ammeters in C3 Corvettes are kind of bogus in that it's actually a volt meter reading a voltage drop across part of the harness. Back in the "old days", the ammeter was in series between the alternator and the battery and had its own internal very low value resistor to generate the voltage drop.

jrzvette

Thanks to all for your replies and suggestions.