[0dyfamily]

On board electronics bog down (a/c blower, interior lights, head lights, etc) when I turn the wheel especially in reverse.

Power steering is a weird beast. Normally, with a hydraulic system, there is less load on the belt when turning the steering wheel, as the fluid is not recirculating through bypass and back to inlet ...

... but we 9th Gen Civics have the even weirder electric power steering. There's more load on the alternator (and ergo more load on the serpentine belt) when turning the wheel.

... from a bit of research I'm leaning toward overcharged/damaged alternator, bad battery, or something else that's gonna cost me more than I wanna spend. High output alternator? New battery? Faulty wiring. Grounding out? I don't know where to start testing.

Let's say you're running at half the amplifier's rated capacity (let's call this a continuous duty cycle?). 600W. At 13.2V, that's 45A.

I don't know what the rest of our Civics use for steady state operation (EFI, spark and everything else on the CAN bus), but I'd guess that 35A or so, give or take a few, is not unreasonable.

Add A/C and lights (as well as turning the steering wheel), and you can add more ampere draw.

I'm willing to bet that the stock alternator is only about 100A, and your total load of music, A/C, and lights is way past the continuous duty cycle for the stock alternator.

A friend suggested the issue could be my battery ground not being a sufficient gauge to handle the additional load ...

Stock grounds tend only to be big enough to support the original vehicle electronics, plus other possible electronically supported OEM options. I recently fixed grounds on a Nissan Altima V6 by cleaning up the stock grounds and adding some 6 gauge cable with crimped lugs between a threaded boss on the transaxle and a welded threaded boss on the unibody.

OF

 

[0dyfamily]

Yes, your friend (and installers with his knowledge) convinced me that even if I had a great ground path from amp to frame (or unibody), that still needs a path to the alternator (and/or negative side of the battery).

So, I did go with an additional "thicc boi" ( 😄 ) cable from frame to engine/trans, and brand new three-lug cable from battery to frame to engine/trans. All contact points sanded to shiny metal and then coated with dielectric grease prior to installing nuts or bolts. Once done, I sprayed these with Corrosion-X to make sure the grounds kept grounding, no matter what happened regarding rain dirt or low flooded areas.

OF