Hi Folks- Every time I have heard this noise in the past it meant a shorted diode and a soon-to-be kaput alternator. I had one once go up in a plume of smoke. Problem is, it doesn't always make the noise. Of course, it sings more at certain engine speeds but sometimes it is not there at all.
I put a digital volt meter on and have over 12.5v first thing in the morning. As soon as I start it, I get 14.4v and, after a while, I see 14.5 or so. Turning on the lights drops it to 14.1. In other words, other than the noise, no symptoms. I plan to clean the battery posts in a minute, just because it hasn't been done in a while. Any other ideas?
Thanks!
PoD