Hi John,
The later generator cars equipped with regulators were a bit of a holdover
with the ammeter. Prior to voltage regulators, many generators had a 3rd
brush on them that was moveable at the generator. You moved it in cold
weather, winter to increase the charging rate and take care of the extra
load of the headlights and heaters. Then the ammeter showed whether or not
the battery was being undercharged with the gen. or overcharged for that
matter. You could easily boil a battery with overcharging, or not start
your car in the morning with a long period of undercharging. Either way it
was at least a nuisance and in the case of boiling, potentially a new
battery.
With reliable regulators, most cars went to the "idiot" light. This was
usually OK as a decent warning device, but was pretty short of display
information. If it glowed at idle, you just speeded up the engine till it
went out and then you knew charging was taking place. When the alternators
came along, the idiot light was good enough. Alternators charged at a much
lower RPM than generators, with the switch to rotating fields and stationary
fields, the brushes carried a very low load and were made much smaller and
lasted infinitely longer. That along with improved reliability of the
diodes, they are virtually trouble free
A voltage gauge will let you know when the battery is low on voltage, or the
alternator is starting to fail. Because alternators are generally so
reliable, a voltage meter is hardly needed. An idiot light will usually be
all that's needed.
Hope this helped some.
Regards, Paul A
----- Original Message -----
From <John.Deikis at med.va.gov>
To: <spridgets@autox.team.net>
Sent: Monday, November 17, 2003 8:21 AM
Subject: Ammeter vs voltmeter
> ...got me to thinking....
>
> Can someone help me understand why around the time of cars switching from
> generators to alternators, cars that actually HAD gauges switched from
> ammeters to voltmeters? They seem to give very different information.
Why
> not both? I have on several occassions been forwarned of a problem
lurking
> when my ammeter read 'minus' after I turned off the key...or even while
> driving around.
>
> JD
> ........
>
> The ammeter does require heavier wiring
> so why not a simple voltmeter? Just a
> respectful suggestion for an easier hook-
> up which will give you some decent
> "information".
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