Alternator Whirring?

[Glade]

Is increased whirring from the alternator a bad thing?

Could it just be that the battery was a bit low (left it 3-4 weeks without the trickle charger on), so it was just working harder than usual?

[AdiT]

You won't normally hear whirring from an alternator under charging load, just an effect on idle speed and possibly squeaky belt.

Whirring is normally associated with the bearings failing. Try listening to it using a screw driver on it and the other end against your ear. It should be obvious if it's noisy bearings.