My alternator died a week ago in my TE and it had the Mitsubishi Branded alternator. I picked up a reconditioned Bosch Alternator and it works fine, except for the dreaded alternator whine. I've had it in the car for a week now but it still makes that noise. The belt isnt too tight and has the proper amount of slack.

I've read around and apparently it can be the bearings and I've heard Bosch alternators are loud as well. I have no clue to why it would be making such a noise.

I'm uploading a video as well if that helps.

Thanks!

Alternator whine is electrical, nothing to do with belt tightness, rough bearings, etc.
Do you have the piggyback suppressor fitted to the alternator?

If you are hearing a whine under the bonnet, rather than over the radio, that's another matter. How much slack in the belt, and have you put a stethoscope on it?

It doesnt have a suppressor, I'm hearing it under the bonnet not over the radio. I havent used a stethoscope but it's very distinctive where it's coming from and it's the loudest at the alternator. Before I changed the alternator it never made such a sound :(

About a quarter of an inch slack

The whine is physical, its from the moving parts in the unit, you can try a rebuild but IMO its not worth it.

I replaced mine with a brand new Bosch, same problem, I can still hear mine from in the cabin, tried all sorts of suppressors but then I spoke to an auto elec and he explained to me how an alternator works and I came to the conclusion that its not worth worrying about.

You will get used to the noise, after a while you will forget about it.