My 99 Accord V6 has and electrical problem at idle speed. Headlights, wipers, interior lights - everything dims or slows down when the car is idling. When the engine revs just a little, everything returns to normal. There's also a little bit of a whine I can hear while the problem is happening.
The battery did test low and due to its age it probably needed replacing. So I replaced it. But low-rpm voltage is still low. The problem still exists.
I've got my eye on replacing the alternator, but I understand there's also a voltage regulator part that tells the alternator when/how much/if to charge.
How can I figure out what the problem is without throwing darts with my money?