Hi Wayne,
The ammeter should never be wired in series with the alternator because then
it will indicate the current output of the alternator - and that's not what
you want. Normally, you would use the ammeter to measure the current flowing
to and from the battery so that you can see whether it's charging or
discharging. In order for the circuit to work as expected, you need to wire
the alternator output (battery lead) to the fuse block, and then the ammeter
gets wired between the fuse block and the starter solenoid. This way, the
ammeter sees all the battery current except that used to start the engine.
However... Ammeters dissipate a reasonable amount of heat, and they have
some plastic parts in them. The problem is if you have any wiring deficiency
in or near the ammeter, such as its terminal connections to the rest of the
wires, it will get HOT, melt the plastic parts, and potentially leave you
stranded sooner or later. I did a test a while ago where at 30 amps current,
the ammeter was dropping about a volt, which means it's generating heat like
a 30 watt light bulb. The reliability of the ammeter would be significantly
improved if a heat sink were connected to the two wire leads (not shorting
them out in the process), and if the connections were periodically checked
to make sure nothing was getting loose.
Period-correct (more or less) voltmeters are available from Rick at SS, I
believe. They wire in to the ignition circuit (white wires under your dash),
and don't draw any power to speak of. Because of lead-acid battery
chemistry, the ignition voltage is a very reliable indication of the
charging system's performance - if it's between 13.2 and 15 volts things are
as they should be. If it's 8 or 10 volts when the engine is off and the
ignition is on, then you've got a dead cell, and if it's over 15 volts then
the regulator is not working and you should get it fixed pronto before you
wipe out other system components.
Best regards,
Theo
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