alternator noisy under loaded condition???

My 90 348 has a ND alternator on it.
when letting the car sit for days and then starting it
up from cold, I'd get this like what I thought was a
bearing noise from the lower driver side of the engine.
like a rattling noise.
I was concerned that it was timing belt related but the
noise would go away in less than a minute or so.

first I changed the idler bearing for the alternator.
that fixed some of it.
yesterday I removed the alternator belt and started
the car from cold and the noise wasn't there.
I put a battery charge on the battery and replaced the belt
and restarted the car, it didn't make noise.