[Badpuppy]

Ammeter is connected only between generator/alternator and battery. Horn and lights have no influence on it. Early models also had the coil connected on the battery side, but that adds only about 4 amps to the reading. FSB 11/29 moved the coil wire to the generator side of the terminal block on all cars, so the coil shouldn't register either.

Ammeters don't often fail, but I suppose it's possible. I would suspect the battery, although it seems good. Easiest part to throw at it, though pricey. But you could let the dog sleep for a while unless you find some kind of short-to-ground between the ammeter and battery, which could be dangerous.