On 7/4/13 10:44 AM, Randall wrote:
>> I am considering replacing my amp guage with a voltage guage
> If the reason is that you are installing an alternator that exceeds the
> capacity of the stock ammeter; may I suggest keeping the ammeter and adding
> a shunt to recalibrate it?
You may, but I do not think it is the best solution. This is one of
those very rare instances where I have to disagree with Randall. I
believe that a voltmeter can tell you more about the health of your
electrical system and if it is being overloaded than an ammeter can.
An ammeter will tell you if the current is flowing into the battery or
out of the battery and how much. The small car ammeters are mostly
gross indicators and do not read small amounts of current flow well.
When I moved from Seattle to Monterey I drove my 1968 Land Rover along
the coastal route. It was a cold stormy trip down the coast. I had the
headlamps on, the windscreen wipers on and the heater on high all day.
The ammeter looked fine but next morning my battery was too low to start
the engine and I needed to use the hand crank instead of the starter
motor. The electrical drain was just a little more than the generator
could produce. Not enough to cause a noticeable deflection in the
ammeter but enough to slowly drain the battery. A voltmeter would have
caught the overloading right away.
A voltmeter will tell you when you generator/alternator is not healthy
because the voltage will read lower. It will catch worn brushes and
overloaded circuits. It can catch things like corroded poor connections
that reduce the voltage in the system.
Right now the alternator is going out in my 1960 Land Rover. The
voltage is lower than normal but there is still enough to keep the
battery charged. I check the electrical connections because corroded
connections can cause low voltage. They are fine. I'm keeping a close
eye on the voltmeter to determine when I need to change the alternator.
An ammeter would never catch this until the alternator completely
failed. If the alternator voltage drops another 2 volts it will not be
able to keep the battery fully charged. An ammeter would not catch a
failure mode that doesn't quite keep the battery fully charged.
Both my Land Rover and my TR3 have Lucas voltmeters. Last time I looked
they were still available new. With the TR3 I swapped the bezel ring
and the curved lens from the ammeter to the voltmeter.
I would never go back to an ammeter again just because a voltmeter can
tell you so much more about the health of your electrical system.
TeriAnn
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