[noahsdad]

Not stumped, just seeking similar experiences. Recently I noted a slight buzzing (mechanical, not electrical) from the engine compartment that follows RPM, in gear or not.
Tracked it down to the serp belt area. Doesn't sound like it's coming from the air pump, the alt and AC compressor are fairly new - so I'm thinking either the tensioner or the PS pump.
Opinions welcome.

 

[Ranger]

There should be an idler as well I believe.

 

[chubbyranger]

Read in another post that you used AC Delco replacement alternator so probably not that. I had 3 of Napa's finest rebuilts go toes up in <2 years on my CDV. First lasted 2 days and pulley bearing disintegrated, 2nd went one week before charge light back on, third had bad voltage regulator (lights flickering). Also replaced tensioner pulley for noise at some point. Alternator #3 or water pump #2 - they all run together after awhile. My PS would moan but only when turning the wheels. Early water pump bearing noise? That's another one that bit me in the a$$ for using aftermarket rebuilt junk. Never again.