GM-GMC: 2000 S 10 chevy, model gm, wire connections

Question
My 2000 S10 volt meter fluctuates at idle {600 rpm} 14 to 12 volts back & forth a few times. I can make this happen whenever I want. I push the accelerator to increase rpm to approx. 1200rpm. As rpms are coming down to idle, volts drop down to 12 volts, eng. returns to steady, volts return to 14. But this symptom is most noticeable at idle. Lights dim for maybe two seconds at 12v, lights return to normal at 14v. It acts like it has a quick amp draw, this has no effect on vehicle performance that I can see or feel. It always returns to proper idle & accelerates just fine. Note:  alternator was changed due to BRG failure. It had this problem before & after alt. swap. My vehicle has approx. 95,000 miles, this symptom has been happening approx. 35,000 miles.

Answer
This could be anything from corroded battery and/or ground wire connections to a battery going bad to a slipping drive belt.

Late model GM alternators will not charge if the battery voltage falls too low.

I cannot be more specific about an answer because there are simply too many things to check as possible reasons for your problem.

A diagnosis at a shop may give the answer.