Reacently my rpm and alt needle started to fluxuate while standing still the thing i cant figure out is why cause im running a hifonics brutis 2005d amp but only useing 650 rms but the fluxuation only happens when i have the volume carnked half way with lots of bass but it dosent affect my lights at all no dimming no nothing and i have a new battery what do you thing time for that new alt
With my car, the needle sometimes fluxuates while idling, but I'm pretty sure it's because I've just started using mobil 5000 synthetic oil.
anyways, it could be things not related to your electrical system. It could be a dirty fuel filter, clogged air filter, plugged catalytic convertor, bad O2 sensor.. could be a number of things... and the things I've listed meet your symtoms.
I'd first bring your car up to an autozone, and have them hook up to it.. they can do a free in car test and tell you if it needs to be replaced, same with your battery. If everything checks out good (more than likely will, and make sure to go to a couple different autozones) then you know it isn't your electrical.