chirping alternator

Keep your eye on the charging voltage and if it keeps jumping around without settling down it needs to be replaced before fails completely.

I had same problem on my w22 8.1 replaced belt noise gone for 3 months than back again replaced tensioner ass. never herd noise again

The electrical output is fine. Just makes annoying chirp when cold at low speed.

The serpentine belt does run the AC compressor, the power steering pump, and the water pump. With the belt removed, all other things are smooth, free running and no noise. I can make the alternator make a small squeak when turned by hand, but does not seem to be a bearing. I really don't want to buy a new alternator if I can find a way to get rid of the chirp.

Check belt and tensioner. Both may need replacing depending on age. Don't use any type of belt dressing as that is a waste of money.

Had the same on my 8.1, the belt only had 25k. but 7 years old Replaced belt and all was good. At about 30k another noise but turned out to be the idler pully bearing

If you can make it squeak by turning it, you have a bad bushing and the alternator needs replaced. Its 10 years old. Id do the belt and tensioner at the same time.

For testing purposes only, rub a bar of soap on the belt for the alternator. (I have to say it....WITH THE ENGINE OFF)

If the squeak goes away, then you know it is the belt. If not, then you need to look at the alternator itself.

Mick....The belt tensioner was a common problem on that engine. I believe you can see it/access it via the passenger wheel well. Spray some WD40 on the tensioner when the engine is cold and see if you still have the problem.

When you first start the engine up, the alternator is creating a LARGE drag on the belt because it is trying to recharge the batteries from the starting draw. When it is not producing the maximum amount of power, such as when the engine has warmed up or you are turning it by hand, then there is hardly any drag. I would guess that your alternator, when the engine first starts, is taking 20 HP just to provide the 145 amps of charging current.
I doubt it is a tensioner problem although it could be a glazed belt. They make spray on belt dressing that you can use to check for belt slippage but I would just get a replacement 108" Gates belt, not a Dayco, and change it. I would also not discount an alternator bearing if the noise continues.

I recently replaced the 2 idler pulleys and belt simply due to age. This noise has come up since then. I have tried to get the tensioner to make noise an d cannot get it to make a peep. It is still strong and smooth to move. I even took it off and sprayed the inside of the tensioner works with Kwiklube. Reinstalled it with no difference.

I guess I will just have to bite the bullet and change the alternator. Will probably give up on it for now and deal with it early next year.

Thanks for all the suggestions. -- Mick