1988 Ford Ranger replace alternator, new sound?

[SolusUmbra]

I replaced the alternator on my 1988 Ford Ranger 2.0L and now it sounds like a tea kettle. Wonder if anyone else can hear the whistle and know what it might be.
Link to my Reddit post that has a video https://www.reddit.com/r/MechanicAdvice/s/QL91hviZUA

 

[Nukeman7]

Mechanic checked my new alternator and said it was fine

I'm thinking your mechanic is likely wrong and doesn't want to redo the job. Common sense says if the noise wasn't present with the old alternator, but is present with the new alternator installed, it's highly probable coming from the alternator. There is also a chance that the belt is too tight and overstressing the idler pulley. In any event, the squeal leads back to something the installer did.

 

[fdcg27]

I’m the one would bought and installed it, he stopped by for free to make sure I had my belt tight enough (I did not) and to try to hear the sound, but either I don’t think he could hear it or he wasn’t sure what it was. He told me to keep an ear on it and let him know if it got worse.

This might be your bet bet.
If something is wrong and is causing this new noise, it will quickly get worse making it easier to find the source.
If it does turn out to be the alternator then you should have warranty coverage for it.

 

[bdc101]

What kind of tensioner did these use?

I had a car that had a tensioner you would tighten with a nut. But haven't seen one of those in a long time. Could be just as simple as being too tight. But it could also be a bad alternator -- which is absolutely possible even with a "new" part if you didn't buy it from a dealer.

Use a stethoscope to find the source of the noise, or my personal preference: a few feet of vacuum tubing.