Voltmeter needle unstable

Sorry for the late reply.

If your talking about the voltmeter on the dash. I'd use a digital multimeter at the bat terminal at the alternator, engine running. See if the reading is the same as dash reading. I've seen voltmeters move with operation of any electrical system. On some makes and models, I've seen the voltmeter needle move in time with the turn signals flashing. Is your idle stable? I haven't looked at your alternator wiring to see if computer controlled? Check voltmeter wiring.

I realize this is an old post. In the future, hope you don't have any vehicle issues, but, if you do, keep the site in mind. They are always working to improve the site and it's free to ask a question.

Have a good day.