Hello John Best, I just read your Post regarding "Ammeter".
You have several questions hidden in your Posting;
You also made a wise move by Posting to (2) separate Lists
The WT & the MV lists - nifty devil, you !
Let me state that these ammeters are not really accurate at all. Not. Not,
Not !!!
If you could put 5 amps then 10 amps then 20 amps through the same ammeter,
Do not expect the needle to move, for instance, in the same equal
increments.
I have seen many different meter scales.
-15 - 0 - 15+ or -30 - 0 - 30+ or so on, you get the
picture.
However, that said they do a reasonable job of showing a charge [+] or
discharge [-]
Here is my take on the 6 Volt versus the 12 volt ammeter.
Basically they are not voltage sensitive as they measure the current [in
amps] flowing in a circuit.
Whereas a voltmeter measures a voltage across an two wires or battery.
However, an ammeter is pyshically inserted in between the battery and it's
circuits as opposed to measuring across the (wires or battery) circuits as
in voltage measurements.
Now to your question "Is the there a 6 volt ammeter or a 12 volt ammeter ?
Well YES and NO and here is why thanswer is confusing in our MB's
GPW's - Willys or Military Vehicles.
Electrically speaking we need to look at the two system and then it should
become clear what the difference might be.
If you have an Ammeter designed for a 6 volt Willys and you turn on the
headlights and your headlights are of a certain brightness usually rated in
"WATTS" then the needle of the ammeter that was designed for that jeep may
move, for example 3/16ths of an inch. towards the [-] Discharge
direction.(engine not running)
If you take that "very same" good ammeter and put it into a 12 volt system
and the headlights are rated at the very same brightness "rated in WATTS" as
the previous 6v example then thevery same ammeter needle may only move just
a very small amount ...possibly 3/32nds" or less.
So why then, would the very same ammeter register differently on a 6v or 12
v sytem using the same brightness or "wattage" Headlights. (Of course on
your jeep, you would change from a 6v sto a 12v lights)
It's simple, If we were running two 6 Volt - 50 watt headlights (100watts)
you would need 16.6 amps to operate those lights.
The 12 Volt - 50watt headlights (100watts) you would need only 8.3 amps to
operate the new 12v lights
Well I'm sorry to have taken so long to get to the final point however, the
needle may just barely move when that original 6 volt system ammeter is
operating at 12 volts.
In other words for a given wattage... twice the volts equals half the amps.
If you tore apart an ammeter designed for 6 volt - amperage requirements
...and
then tore apart an ammeter designed for 12 volt - amperage requirements...
You would probably see a couple of turns of much thicker wire in the old 6v
ammeter due to the need to pass (basically) twice the current.
Finally, without getting out all you test gear just yet ..run the engine at
a low idle with the headlights on ( 6 volt generator system) next rev the
engine... when the voltage regulator "cuts in" the light should brighten.
"Houston we have a charge" !!! Check it out.
NOTE Some alternators can charge at much lower revs tahn a generator so the
above check may "not" work as described.
Gordon Mcmillan on thew mil-veh list, said it nicely in an earlier posting.
I copied and pasted his info. I hope Gordon doesn't mind.
(Snippet - Gordon wrote)
Well if it shows a discharge when cranking and a discharge when running
it's hooked up right and either the generator, voltage regulator, or other
wiring is at fault.
If it shows a charge when cranking and a discharge running you may have it
wired wrongly.
So, Swap the two wires over on the back of the ammeter. If theres more than
two it should be the thickest two - to start with
Sorry for the length of this
Aussie Rob
A thing to note is that when I first got my '42MB someone had already put in
an alternator.
Damm it I thought ! This thing barely charges at all ???
OOPS upon further inspection, we had exactly the problem I mention above.
The current at 12 volts barely deflected the needle - I mean just barely.
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