Altenator diagnosis questions, whining noise when warm
Ok, to start: 2005 330ci ZHP, 120k miles, 6 spd man
So here is the story, my car is running great, no dash lights of any kind. When warmed up, I have a subtle whining noise. Gets a little louder with higher rpm, but doesn't really track with rpm. Intake boots are in good shape. The belts and idler pulleys are all new. I can't quite seem to tell where the sound is coming from. One thought was the power steering pump, so I figured a good flush with new fluid plus replace the reservoir because it has a filter and the cap o-ring has failed. No change, still a slight whine when warmed up. I did freshen up the tranny fluid (manual) and diff fluid at 100K with Royal Purple.
I did some youtube searching and ran across this vid:
https://www.youtube.com/watch?v=72REiFhvNuE
I got my voltage meter out to do some testing. My altenator is pushing out about 14.5v and it drops to about 14.2 when lights and accessories are all on. When I switch from DC to check AC as described in the vid, I have 75mV AC. So, I'm not at 50mV, nor am I over 100mV.
The other oddity is my alternator does not have a cooling shroud on the back and thus no snorkel as I had on my 325 and as shown in real OEM. The PO maintenance records show no evidence the alternator was ever replaced (could be missing record). I neglected to look and see if it was Bosch or Valeo, or something else.
Thought I would tap into the collective wisdom here:
Is the information in the vid a valid diagnosis?
Am I looking in the wrong place?
Any other thoughts on where this noise may be coming from?
