I have a 300D that makes a squealing noise, similar to a drive accessory belt. I replaced all 3 belts with high quality ones with no change. I later noticed the noise was much worse when I was using electrical systems with large draws (headlights, heat, A/C). I replaced the alternator and it seemed to do the trick for about a week, then it started again. It doesn't make the noise until it's above an idle speed, and when it does, it's impossible to diagnose where it's actually coming from just from the sheer volume. Has anyone here experienced the same issue (and figured it out)? Thank you in advance.