Everything Tony said is true, but here is the flip side to the
argument, which I include for completeness
:
First, it is easier and less risky to hook up a voltmeter than an
ammeter. With an ammeter either you run all the current through the
meter (and its internal shunt) or you have some more complicated
shunt-like arrangement. It isn't going to be easy like checking
voltage is. Even discounting the starter cable, which probably won't
be part of the ampere reading, there can be quite a bit of current
through the meter -- and it is current that you don't want to
interrupt, like your headlights and wipers. So you want the meter
wiring to be sturdy and reliable.
Second, if you had an accurate voltmeter (which most automotive
voltmeters aren't good examples of) you could tell the condition of
the battery and whether it was being charged or not. If your
voltmeter can be read to tell if it is measuring 12, 13 or 14 volts
then a voltmeter can be quite useful. You may have to discover what
part of the scale each of these voltages is indicated on your
voltmeter, but it can probably be done with decent quality automotive
equipment. So you are 'calibrating' it yourself.
The choice is yours,
-Roland
On Fri, 22 Jun 2007 19:11:14 EDT, you wrote:
::Bruce,
::An ammeter (amp gauge) will tell you immediately if something is wrong. The
::needle in the positive zone indicates that amperage is flowing into the
::battery. That tells you that the voltage regulator and your generator (or
::alternator) are working. If your battery is found to be dead on occasion
and your
::ammeter is always in the positive zone while the car is running, this
typically
::indicates that your battery cannot hold a charge and hence the battery is
the
::most likely the problem* . When the ammeter stays in the negative zone,
this
::indicates the battery is discharging. This typically indicates a faulty
::generator (or alternator) or voltage regulator. When you see an ammeter in
the
::negative zone it is only a matter of time before your battery will be dead,
but
::in this case the battery is most likely not the problem, since the battery
::is not receiving a proper charge while the engine is running.
::
::A dashboard volt meter, on the other hand, only tells you the present
::condition of your battery and is not much help in making a diagnosis as to
why your
::battery continually drains. Is it a charging issue (bad generator or
voltage
::regulator) ?? Or is it that the battery cannot hold a charge for long and
::therefore the battery is defective*. Making the correct diagnosis on a
::dashboard voltmeter is difficult.
::
::I personally prefer an ammeter over a dashboard voltmeter for the reasons I
::stated above. For me the ammeter provides greater value since it gives more
::information as to what is happening as the car runs. I hope this
helps....Tony
::
::
::*Providing you don't have wiring trouble, short circuits, or lights that
::remain on when the car is off
|