Most of the cars I have had had their alternators or generators near the
exhaust system, and on one notable occasion my self-installed ammeter got
its wire in contact with a hot exhaust pipe, filled the car with smoke and
made a mess of a bunch of other wiring, also putting the car out of commission
for some time.

The ammeter DOES tell you whether or not you are charging the battery but it
doesn't tell you why not. For example if the battery is fully charged the
ammeter will indicate zero but could be misinterpreted. A good voltmeter will
tell you how well the battery is being charged (or not) and is probably at least
as good a measure of your charging system (especially the voltage regulator) as
the ammeter. Certainly the voltmeter can indicate a discharge also as the
voltage will be less than 12.6.

I am a lot more comfortable with wiring that is carrying less than 1 amp than
with wiring that normally carries 25, 30 or even 50, not to mention the serial
resistance this puts in the charging circuit. I'm really not sure how an
ammeter will give you the state of charge of a battery.

Having installed both and used both for many years I guess it is mostly a matter
of personal preference but given the choice and ease of wiring, I'll henceforth
go with a voltmeter every time, and when I work on the 164 (replacing dash and
heater, etc) you can be sure the ammeter will come out and be replaced by a
voltmeter.
--
George Downs, Bartlesville, Heart of the USA!