2004 Chevrolet Trailblazer Q&A

2004 Chevrolet Trailblazer Question: What is the problem when gauges are erratic up and down?

I got a new battery and checked alternator -
Answer 1
maybe there is an electrical issue -
Answer 2
Ihad an alternator installed but now the check gauge come on and and the battery gauges drop all the way down whwat you yhink the problem is?my truck is a 2002 dodge dakota 3.9 engine -