My rebuilt Bosche has a high-pitched whistle, particularly at low RPM.
I disconnected the wires, and the whistle stops completely - so it's
not mechanical. It turns smooth and functions fine.
I installed the unit 2 years ago, and I thought the whistle would go away after the brushes broke in. But now it's starting to bug me.
Any suggestions, rather than get another unit?
maybe replace the regulator? Maybe replace the capacitor on the housing?

Tks,
DG

Is the whistle there all the time or is it intermittant...If it is intermittant I would suspect you have bad bearings in the alternator. The reason it would be intermittant is that the alternator is not always under load and will only whistle when the battery is calling for more current and voltage. When the car calls for current and voltage the alternator wants to go in the opposite direction that the car is causing it to go so if there is tolerance in the bearings it is possible that it can make this noise....it is possible also that the whistle is the voltage regulator but this is less likely...my 2 cents

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2005 Honda Element 266,000
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http://www.peachparts.com/shopforum/showthread.php?t=125099

Thanks. Good point, under load it could aggrevate a bearing.
It does do it all the time, but hits its best falsatto at certain narrow RPM ranges, loudest at approximately 1000 RPM. I pulled the belt off and spun it and yanked the armature back and forth - no slack, no noise.
and it has not changed in the last two years since I installed it.
I tried a new belt yesterday, but no change.
Maybe for the relatively low price of a regulator, I might try one.
Guess I could add the old one to my emergency spare collection in the trunk.


Thanks again for the inputs.

DG