Alternator gauge is smoking
Key off:
A ground short anywhere after the ammeter should cause the needle to peg discharge. If there is short on the battery side it will not show on the meter.
Another way to put enough current through to smoke wires is with the engine running and a low a battery.
Here's what happened to someone's ammeter wires when they let the engine run for 20 minutes with the ammeter pegged to charge.
Key off:
A ground short anywhere after the ammeter should cause the needle to peg discharge. If there is short on the battery side it will not show on the meter.
Could be a short as 67Dart273 described above
Another way to put enough current through to smoke wires is with the engine running and a low a battery.
Here's what happened to someone's ammeter wires when they let the engine run for 20 minutes with the ammeter pegged to charge.