This looks like something that might be useful to me.
If you're willing, could you please elaborate on the part(s) that you installed and how you did the wiring? Thanks-

Very nice Frank .

The deal with the charge lamp is : your alternator can fail and it won't tell you so you drive on the mechanical fuel injection then the next time you try to start it, nothing .

BT, DT no fun, good thing i wasn't 75 miles down a bad Desert road with no cell service .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

This really isn't a big deal. Any generic voltmeter with a suitable range will do the job. Drill a suitable hole and mount it in the dash. The one in the photo came from a direct-from-China seller on Ebay. This is a similar example:

https://www.ebay.com/itm/LED-Digital-Display-Voltmeter-Car-Motorcycle-Voltage-Volt-Gauge-Panel-Meter-12V/382624102408?hash=item59162c7808:m:mjOteNyJ32wi3AcLHzv4Mzw

A voltmeter has two wires: one goes to any ground, the other goes to any switched 12V source, I think I used the lighter wire for this installation. If you want to be anal, you could run wires all the way to the battery, but it's not really necessary.

As far as reading it. A fully charged battery reads 12.5V. Above 13V means the alternator is charging. Bosch alternators are usually regulated to 14.25V @70F. They will vary from 13.5V to 15V depending on operating temperature. If the reading drops below 12.5V, it means the battery is discharging. There are extreme conditions when this may be ok: idling for a time with the headlights, wiper and heater on, for example. So much more information that you get from an idiot light.

Truly, I sincerely appreciate your willingness to share not only the details of the kind of part and wiring, but also the proper way to read the information.

This will be a nice project for me. Thank you!

Thanks everyone for your responses.

I wonder how hard it would be to either buy or make an electronic circuit that would trigger a buzzer or a warning light when voltage drops below 13V ?

would work better than a voltmeter because you wouldn't have to look down and you would know instantly.

Thanx Frank ;

I don't see what size hole it requires....

The colors thing is nice but, blue isn't so easy to read at night when there's ambient light around...

BT, DT and wasn't pleased .

Too bad they don't make this round one in 6 ~ 24 volts, it'd be very handy for vintage vehicles and ex military with 24 VDC systems .

-Nate

Any opinions about the usefulness of a display that in addition to current (voltage), also displays amperage?

Thanks-