Bulkhead Instrument panel bypass.

As long as the ammeter never grounds out, you are fine. If it grounds to the instrument cluster or internally, you are at risk of the same issues as the charge energy flowing through it. I prefer to not have anything attached to the ammeter.

There are some voltmeters that plug into a cigarette lighter out there. Neat for someone that doesn't want an additional gauge in the car, etc. Plug it in, when you want it out, toss in glovebox, console.