I have a '99 2.0 Tracker with stock alternator and new Optima Red Top.  Digital voltmeter normally reads 12.8 at start up and high 13's |removethispart|@ 2,000-4,000 rpms; but, a high rpms 4,000+ voltmeter fluctuates wildly and occasionally hits 15.2.  It drops to approx. 12.8 and back up to 15's and everywhere in between.

Is this indicative of a problem?

Thanks

You have are a couple of replies over in the other forum ...

Presumably you have already checked for loose and corroded connections.

Try driving at night and see if the lights flicker along with the variations on the voltmeter - I'm thinking that at the higher rpms you're getting electrical noise that is overwhelming the digital voltmeter and causing it to indicate erroneously - if the lights do flicker then toss my theory out.