Nicole

Another question regarding these alternators... I had this alternator replaced some time ago because of a whining noise. We reused the pullley, though. And the whining noise persisted - even after changing the belt. Can the pulley cause a whining noise? (This is independent from the rattle discussed here; in fact, the rattle drowns it out when it happens).

Mrmerlin

Nicole i would suggest that you fix the alternator first, then do the remove all the belts and add them back on one at a time your whine may be from something else like the timing belt tensioner roller

Nicole

We've already done that, and we know the whine disappears when the alternator is disconnected. It has not changed between old and new alternator as well as old and new belt, so the common denominator are the pulley, and the cover in the back. However, the whine can be heard strongest in the front.

I had suspected that there might be a misalignment between alternator and crankshaft pulley, but I can't really see how this could happen. How much is a pulley like this? Probably not out of reach, but I'd like to know, if there is even a chance it would end the whine....

Mrmerlin

Nicole the alternator will make a whine while its working, and if there is a load on the elex system then it will be louder, I think the noise is the AC current going through the diode boards and being converted to DC

Bill Ball

Nicole: I don't hear that whine anymore. It did still whine initially, but I didn't notice it recently.

Nicole

It's still there - just overshadowed by the much louder rattle

Bill Ball

What I used to hear was more of an air whistle than a mechanical/electrical whine. Your alternators have had a different external fan than mine.

SteveG

The S4 has external fan on the alternator?

Mrmerlin

the fan in question is just behind the pulley ,it sucks air in from the back to the front of the alternator, in fact this is how most alternators are cooled

Bill Ball

Yup. My original 89 factory alternator had a common pressed steel fan, as did the replacement alternator, whereas Nicole's 91 alternators have both had cast aluminum fans.