So I had my battery tested and my alternator tested. The results at advanced auto parts said that my battery was bad, so I bought a new one. Even after a new battery and the test results saying that my alternator was charging the battery correctly, my alternator is still whinding(after the new battery it whines less) and my battery gauge still moves back and forth when the truck is at idle. My lights still get brighter as I accelerate(this symptom is also lessened after the new battery). Does this mean my alternator is possibly dying or struggling? Any ideas? Thanks.

 

Be sure to check all your battery cable connections, both ends, battery and terminal.