fwiw, I had a 2002 Roadtrek upfitted into a 3500 Chevy Express Van. I got around 180,000 miles out of the original alternator before it finally gave up, and one of the symptoms was a battery indicator light on the dash. I spent about 1/2 hour in a rest area on I-90 in Montana checking the chassis battery connections and everything else I could test, until I finally decided it wasn't the battery, and took it to a GMC shop in Billings where they replaced the alternator. No problems after that, batteries and alternator lasted another 30,000 miles until I sold the van.
Good luck with it.
