Hey everyone, my trucks been having a problem the last couple days. Sometimes when I'm driving, my charge light will come on, and the voltmeter would drop in it's reading. The first time it happened, I thought I threw a belt, so I turned the truck off and scoped out the engine bay. Well, nothing looked out of place, so I started the truck up, and everything was fine, no charge light, and a correct reading at the voltmeter. But after driving for about 20 mins, it came on again. I thought it might be a lose connection on the alternator, but everything is tight. So I was just wondering if it's possible for the alternator to be intermittent, or is an alternator either dead or working, nothing in between?

Thanks for any help.
-Nick