Got a 'whine' coming from the driver's side of the engine which I tracked down to a specific pulley. Bought a new tensioner because I thought that's what the pulley was attached to, but it isn't. Got the whole car in pieces before discovering that the suspect pulley is actually mounted on the alternator mounting bracket (which I removed because it's easier to get the tensioner off that way). Turns out at least I had the right pulley - the bearing is shot, wobbles like hell and makes a grinding noise when I turn it by hand.
It's a ribbed pulley, about three inches in diameter - as you look at the aux drive system it's the very top pulley, right at the back, above the alternator. I need to get a replacement Monday but not sure what it is I'm asking for. Any ideas?
 Checked the Haynes manual, which, unhelpfully, refers to it as "idler pulley". There is also another idler, non-ribbed, slightly bigger, also called "idler pulley".