Buzzing in speakers, 2002 V6 with JVC Unit

I installed my entire system myself, but I had alternator whine show up after making no changes to my system.

It turned out that my electronic crossover moved less than 1/8", as there was insufficient strain relief in the RCAs (my first install, newb mistake) and they tugged it over a tad. When it moved, an RCA cable connector touched a protruding bolt near the install location. That caused a ground loop, thus the alternator whine. I relocated my electronic x-over, and my install has been silent since then.

You didn't change anything, but that doesn't mean something didn't change (obviously). Hopefully your installer will take the time to find this new issue without wanting to charge you for their time. I expect you have some kind of warranty period on the install, so you should be fine as long as the issue is actually found. Only took me a couple minutes to find mine though, once I started looking.

Good luck!