Alternator Screech?!

Ok, ever since I got my truck the alternator has been making the obnxious squeel in cold and wet weather... Now its been raining here in philly for like the past 4 days and the sound is getting worse. I dont think its the belts because I replaced them when I first got the truck. My dad says it could be the alternator bearings??? and idea if thats what it could be? and if I have to replace the whole alternator? Im not sure if the alternator is sapose to be hot, but mine is gettin pretty hot. Its gettin so loud I can hear it over mt ehxaust and my radio ( when its relativly low). It seems to get more high pitched when I accellerate until about 3000 rpm. then it either goes away or shifts and starts over.

Any ideals?? I really want to fix this this weekend. Thanks.

Are you sure it is the alternator and not the fan belt? My old truck had the same symptoms and it turned out to be the fan belt sliping due to a weak tension pully.

A quick test to see if it is the fan belt is to put a small amount of grease or WD-40 on the belt and then start the motor. If the sound goes away, then it was the fan belt.

Its possible.... I replaced the fan belt when I first got the truck. It was the afctory one and it should of been replaced at 60k, I got it with 59k. It made the noise on the origonal belt too, just its been getting worse in the past month or so. But ill give it a shot.

Any other suggestons??

Grease or WD-40 on a fan belt ????
Why on earth would you do that, all that would do is make it slip more not to mention the grease being a petrolium based product will eventually rot out the rubber of the belt. plus you now have grease or WD-40 in all of the groves of the pulleys, small amount or not I still say it is not a good idea. The best thing to use is actually belt dressing but why go and buy a product that you will hardly ever use right ? The cheapest way is to take a bar of soap and with the vehicle running CAREFULY rub the soap on the belt. Do this on all the belts , just on the bottom for "v" belts and along the top as well for the serpintine belts because these belts run against pulleys on both sides of the belts. If this causes the noise to go away, problem solved and if your belts are in good shape, no cracks or or anything like that then no need to replace them just once in a while if the noise comes back, reapply the soap. My dad has done this for years and even I have done it and never have had any problems due to using the soap. I have even had belts that have made odd clicking noises that the soap trick has solved.

Yea, along with the squeeling i can hear like a rotation noise... I donno how to describe it...it just sounds shitty. I might actually have some of that belt dressing stuff. My dad has a whole garage full of junk, im sure theirs some.
So no one thinks its actually the alternator?

Oh it could very well be the alternator. Quite possibly a bearing, sometimes they whine if the voltage regulator is going. I had an 88 fs jimmy once and the regulator went and it was whining real loud but it was also charging at something stupid like 18 volts. It is a good thing that it happened in the middle of the winter or it could have blown up the battery. It almost sounds like you may have a bearing going bad. You should be able to buy a rebuild kit that comes with bearings, i know for my 96 i was able to anyhow. It is just that the belt is the first and easiest step in the process, it is not like you would want to rebuild/replace the alternator and have it still make the noise. Easy way to find out if it is a bearing though , take a metal bar approx 2-3 feet long and with the truck running carefuly place one end of the rod against the alternator and put the other end to your ear, if it is a bearing going bad you will be able to hear it with this method espically if the noise you hear is amplified through the rod.

I can definetly hear a bad bearing without the rod!

I can definetly hear a bad bearing without the rod!


Your ALT is bad. Pretty impressive. Usually the others parts wear-out before the bearings.

Might want to look into getting a POWERMASTER alt. Sweet and you can rebuild them yourself.

I have a 200 amp on my Jeep and will put a 200 amp on my truck when it goes bad.

Your ALT is bad. Pretty impressive. Usually the others parts wear-out before the bearings.

Might want to look into getting a POWERMASTER alt. Sweet and you can rebuild them yourself.

I have a 200 amp on my Jeep and will put a 200 amp on my truck when it goes bad.


I agree, I think your alt. is bad, mine did the same thing but was also throwing metal shavings everywhere. Kinda freaky when you open the hood and your alternator starts throwing stuff at you! :22yikes:

So are you guys suggesting i just get a whole new alternator? or just rebuild it?

I suggest taking belt off and spinning the alt shaft and listen for the bearing grinding,rubble, or any other suspicous noise. But I agree with the fact that your alt. is on it's way out. does it squell louder when you turn on headlights? It will get hot running normal but not too hot. Oh and the bar of soap method works as well as candle wax (for a belt slippage). serpitine belts are pretty good at not slipping.

I had an altenator go on my last vehicle after I helped a guy; his battery was low and I jumped his truck. He didn't wait for me to charge his battery a bit and hit his starter. It fried my alternator, it got louder and louder. The bearings in it were shot, Yeah don't rebuild it just replace it. Don't forget to check your bearings in your tensioner pulley it might be that too...

there is tsb on the alt going bad. i bought a 00 sil LT 2 wheel dr. and it was a gm certifird.2 weeks after started sqealing they replaced under warrenty.

really? my trucks gion in on friday to get the last of the recals done... If you could post or e-mail me the tbs that would be great! maybe i can try to get it done then. The ony thing is that my truck wasent GM certified. But its worth a shot.

I never tried this but, if you take the belt off, can you turn the alt pulley with your hands? with the engine off I think it should turn very easily and you would be able to hear a bad bearing... just a thought