1999 Suburban Volt gauge

I was travelling one day and the volt gauge went to almost 9. Went and had alternator rebuilt - whic it needed. Still had same problem. Had the guy take alt. off again and he replaced something inside - regulator I think. Had same problem with guage again. He took it off to test and the thing is fine. Have not had the needle go down again but am a bit gun shy. I have gotten a few ideas from people (not sub owners) but thought someone out there may have had a similar problem.:banghead: