Alternator noise at 1000 rpm
Can a failing voltage regulator cause excessively loud noise only at a certain rpm, let say 1000rpm? I have been hearing this alternator noise/whine at 1000rpm all the time. I replaced the alternator with a refurbished once last year and the noise is still there. Some mechanics said it's normal sound when the alternator recharges. Why do I only hear it at 1000rpm? The pitch is quite high and I find it really annoying. I have looked into the possibility of vacuum leak and concluded that that's not the reason. Any insight would be appreciated.