I have an ampmeter in my '62 C10 with the internally regulated alternator upgrade.
Hook one wire to the battery terminal on the starter. Hook the other end to the gauge. Hook another wire to the output terminal of the alternator. Hook the other end to the gauge.
Turn on the truck, but do not start it. The gauge should show discharge. If not, reverse the wires at the gauge.
Once that's straight, fire up the truck and run it up to about 1000rpm. The gauge should show a slight charge or nothing at all, depending on the condition of the battery.
It's an easy wiring update.
