Now I will stop at this point.

When driving, I can glance at the gauges, and tell if it's running hot, that I have oil pressure,What the oil temp is,and that the electrical system is healthy.

I do not care what my tail lights draw, and I do not care to know how many gallons per hour of oil is flowing.

Sixfooter and I both specialize in battery back up systems for data centers. We deal with batteries every day.

All the authors in all the threads disagree with you, as do we. All the auto makers agree also.

Go argue with somone else. Ignorance is bliss.

 

Quote:
"A Voltmeter reports the Car's System Voltage which will ideally be 14 Volts at all times. If the Alternator fails, the Voltmeter will drop fast. If the Alternator or Regulator goes overvolt, you will immediately see the Voltmeter's needle hit a danger area on the Gauge.

Because a Voltmeter only places a tiny load on the Electrical System it can be placed quite a distance from the Battery or Alternator and still give an accurate reading.

You can determine the Battery's state of charge by lowering the Engine RPM when the car is in Neutral. If the Voltage drops rapidly the Battery is undercharged. If the Voltage remains high for a lengthy period, the Battery has been recharged.

A Voltmeter tells the whole story, whereas an Ammeter at best can only tell half the story, that is when it isn't being completely misleading"

Thats this guys opinion and you know what they say. Everybodys got one of them.

Lets look at what he says.

"A Voltmeter reports the Car's System Voltage which will ideally be 14 Volts at all times. If the Alternator fails, the Voltmeter will drop fast. If the Alternator or Regulator goes overvolt, you will immediately see the Voltmeter's needle hit a danger area on the Gauge."

Exactly what the pseudo amp meter does. If the voltage is higher than the battery the needle deflects positively. If the alternator fails the needle deflects instantly to the negative. If there is an overvolt there will be an extraordinary positive deflection. But, with the added benefit of actually being able to monitor the charging to see how long and deep the charge actually was.

"Because a Voltmeter only places a tiny load on the Electrical System it can be placed quite a distance from the Battery or Alternator and still give an accurate reading."

Exactly the same on the stock amp gauge.

"You can determine the Battery's state of charge by lowering the Engine RPM when the car is in Neutral. If the Voltage drops rapidly the Battery is undercharged. If the Voltage remains high for a lengthy period, the Battery has been recharged."

If that alternator and regulator is doing its job, I dont think you are going to see any significant change in the voltage.

"A Voltmeter tells the whole story, whereas an Ammeter at best can only tell half the story, that is when it isn't being completely misleading"

Nothing is more misleading than an alternator pumping smoke into a bad battery and you have no indication on the volt meter.

Agreed, they both have their faults, but if I have to choose between them, my choice is the amp gauge.

I`M DONE

 

Sure glad mine does not work...I'd be worried....

 

Don't worry Rich. My Model T has an ammeter, a generator, and a battery. When it's dead, I use the hand crank.

 

Well, I thought I was done, but I see you want to call me Ignorant. Just because I disagree with you is no reason to throw out insults. I really don’t care what you do or how much education you have. I also happen to be an engineer with training in electronics and instrumentation. There is room for civil disagreement but not insults.

 

Talkin the 69....does not bother me one bit....cause I know what's happening when I start the ******...

Rich

 

You are correct. I apologise for the cheap shot.

Feel free to explain to me how an ammeter tells you the state of a batterys specific gravity.

 

What charges a battery? volt..........no
Amps.........yes.
How are car batteries rated?
volts...........no
CC Amps........yes
Battery backups?
rated in amp hours right?
you keep volts, I work with amps

 

If you charge a 12volt battery with 6 volts, it will never attain full charge.
I don't know about your battery, but mine is 12 volts.CCA is capacity when NEW.
Battery backups are rated in VA/KVA

 

My opinion about why car manufactors changed from an ampmeter to a voltmeter?

On an ampmeter, the entire battery charging power is routed thru the ampmeter. Check the wiring diagram.

When autos moved to larger and large electrical systems, with more and more current requirements, the engineers knew they could not continue to send all this current into the passenger compartment, thru the ampmeter, and then back out to the battery. The wiring was just going to get too large, having this large power moving thru the dash area was just getting too unsafe.

(Stated by someone that shorted the stud on the back of an ampmeter in a 1964 Corvette. It instantly melted the wire all the way to the battery terminal on the starter. And melted into several other wires in the bundle. I then had quite a cutting of bundles and rewiring job on my hands.)

So, they went to a voltmeter. Which could just tap, in parallel, into the charging system anywhere, and just indicates the voltage at the battery posts. It shows nothing about current flow, which an ampmeter could show. The voltmeter can generally only show the status of the alternator - how many volts it is throwing at the battery, or with the engine not running, the battery voltage. An ampmeter showed the actual amount of current flowing to the battery.

In the old days, if you observed an ampmeter, you could 'see' a battery aging. If the danged thing never returned to mid-meter after starting, you were going to soon need a battery because that one was continuing to pull current into it. A voltmeter never will indicate this, at least to the accuracy an ampmeter can.

As I said, the move to a voltmeter, in my opinion, was because the engineers decided they no longer wanted to run the high current flow into a guage on the instrument panel. A voltmeter needs almost no current flow, only a tap across the battery + and -.

 

What charges the battery?

Both.

If you don't apply more voltage to a battery than it can generate internally (usually 2.1 volts/cell x 6 cells = 12.6 volts in a good battery), it is not going to charge.

When you apply more than the 12.6 volts, how much current (amps) you can push (with the voltage) into the battery determines how fast you can recharge it. (This is determined by how many amps the alternator can produce - windings, armature, speed of rotation, etc). If you can only produce 1 amp, it's going to take a long time to put 100 amp/hours back into a battery. If you are 'pushing' it with less than 12.6 volts, you will never recharge because you are not overcoming the batterys internal voltage.

And, the 'regulator', built internal to GM alternators, is actually switching the voltage (and current) on and off to the battery several times each second. When it switches the charging power to the battery off, it then 'looks' (measures) the voltage coming back out of the battery. If the battery voltage is low, it leaves the power switched on for a longer period of time. As the battery voltage approaches its 'fully charged' level (I don't know, about 13.3 volts? Someone help me here.), it leaves the power switched off longer and longer. When the battery is fully charged, based on battery voltage, and there is little other load from other things in the car, the alternator is switched off most of the time. And we are talking parts of a second here.

 

I think that a bad connection between the bat. and cable ( happens a lot ) will NOT show up on a voltmeter ( it will stiil show 14 v. ) but no current will flow to the bat. the ammeter would show no charge right?

 

Hell of a time trying to start the engine under that above sequence of events....NO??.......so right off the bat, tery....the above is allmost meaningless......allmost.....

I have not seen any car in decades with a true shunt AMPmeter in it....they all do a derived thingy off the regulators somehow....

jeebus, the last car I had with a generator was my '61 Pontiac, in '70....
and my '60 vette before that.....been a great while....

 

Not exactly. You notice throughout this whole thread, I have referred to this as a pseudo or so called ammeter. The design is such that it is really a volt meter that is installed to read a small voltage change in a circuit that indicates amperage, but does not actually measure the amperage. We really just arguing where to place that voltmeter. There is little current flowing in the wires or the meter. My opinion as to why the auto makers made the change is, the average Joe has no clue what he is seeing, and gets excited when the gauge pegs forty or shows negative, when that may be perfectly normal operation. Just see how many questions we get here on that same score. The standard voltmeter is a little more understandable. But, people don’t watch gauges either so the idiot light has replace the gauge as the most used device plus it is cheaper.

 

I must try another angle on this topic. Over and over the discussion leads to the battery. So let's look at it that way.
Neither a voltmeter, or an ammeter will tell you anything about the battery, other than state of charge.
An ammeter will tell you whether the battery is charging, or discharging.A voltmeter tells you the state of health of the system.
The only true indication of battery state is specific gravity, and visual inspection. Phone company batterys are in clear cases. You can easily tell the health of it visually.
Automobile batteries do not have this feature. As a battery wears/decomposes, sediment forms. When the sediment reaches the bottom of a cell/it's done. That's why batteries fail suddenly, and always have. NO meter can tell you this.
The statement that you can tell this from an ammeter is false.
Only chem state, visual inspection, or a dynamic load bank test can.
So, given this fact, monitoring the health of the SYSTEM is your best guide. A drop in voltage will tell you immediately to check the components of the SYSTEM.

 

The regulator adjusts the field strength of the alternator, keeping the voltage output constant.

 

Actually the ammeter is truly an ammeter. I brought it in to work today to test it and see if it works which it does. I takes about 1.6 amps to peg the needle in either direction. Of course this does drop voltage, about 0.33V, as any device measuring current in line has to drop a voltage by definition. A voltmeter by definition is high impeadance so this is not a voltmeter.

Does anyone have a schematic that I can see how exactly it is wired in the vehicle. Does anyone know where the fusible link is routed in the engine compartment?

Thanks.

 

Sorry for hyjacking your thread. The fusable links are the leads on the starter coming off the battery cable post. I do not know where your ammeter leads terminate.

 

I respectfully disagree. In this case the ammeter can give you indication of battery health. I understand what you are saying, but when you install a new battery and it is slightly discharged, you will see a long and deep charge of a considerable amount of amperage. Every time you start that car you see this play out. As time goes on the time of charge and amperage delivered to charge the battery continues to decrease until the point that the car will start and the charge time becomes quick and shallow. This is a very good indicator of battery health. It is observed over time not instantaneously. That is what I am trying to get across is an advantage that a voltmeter does not have.

 

All together now.... "You say potatoe, I say patato.. You say tomatoe..." This argument can go on forever. The C3 ammeter IS a voltmeter..connected to a shunt (which is built into the wiring harness). Anyway, while big amps DO NOT pass through it, it does provide a measure of the amperage coursing through your C3s "veins". Other cars have voltmeters..which are a direct measure of voltage in the system. Both are informative...neither gives the full story. Why not just let everyone have their preference and quit trying to convince them otherwise? I, for one, will leave mine as an ammeter...because it came that way.