What would make the lights go dim and the amp gauge hand go down then go back up. Had the belt changed and alternator checked. Everything ok 2002 Chevy Siverado?

What would make the lights go dim and the amp gauge hand go down then go back up. Had the belt changed and alternator checked. Everything ok 2002 Chevy Siverado?
Sounds like a faulty ground connection, given what you have said. To check without really having to know much about HOW to actually do it, connect two wires to negative ( - ) battery post, run one wire to some clean bolt on the engine, run the other wire to the chassis of the vehicle. If the problem is solved by this you have two options. Go to a parts store and buy ground straps to replace the two temporary wires and the problems should stay "solved", or better yet, go to a mechanic and have him do the job.