There are 3 belts on the truck (1994 V6, 4wd). The belt that goes around the alternator was not spinning and there was a loud screeching noise. I cut the alternator belt to see what the truck would do with the missing belt. The two remainig belts moved fine without a screeching noise. I then replaced all 3 belts and the noise returned but all belts seemed to be moving. I then had the alternator checked and it was bad. I replaced the alternator and still have a bad screeching noise coming from the belt area. Any ideas on what could be causing the problem

The alternator flywheel? I believe, correct me if I'm wrong, that you are referring to the wheel on the alternator that the belt goes around. The screeching indicates a loose or possibly worn drive belt. As the belt slides instead of engaging, it screeches until the rubber gets hot enough to finally grip. Eventually, your battery will fail to charge. It could be a simple adjustment is needed via the alternator or a tensioner to tighten the belt. However, If there's any question about the age or condition of the belt, better to replace it before it breaks. This would be important so you can see how it wraps around the various components. The folks at an auto parts store should be able to assist you with this.

Screeching could be cam belt and ur electrics windows and indicators check fuses

check drive belt driving altanator and air con it sounds like it needs adjusting

Hi Julie,

If your belt only "screeches" when you first start your engine, the problem is most likely to be related to either your alternator or your air conditioner. Sometimes the bearings in these things start getting worn and cause excess resistance to rotation and will cause a screaching noise that goes away once they are moving. This usually also causes "glazing" on the belt.

Look at the ribbed side of the belt. If it looks "shiny" rather than just a dull black, this is glazing. It may not be necessary at this time to replace anything like the alternator or the air conditioning compressor, but I would recommend replacing a glazed belt and do a THOROUGH check of your pully assemblies while you have the belt off.
Spin all of the pullies (including the tensioner and idler pullies) by hand with the belt off. You should not be able to "hear" them spinning. Any pully or component that feels rough or has a rough or rattling sound when you spin it by hand should probably be replaced.

it could be the tensioner, water pump, alternator, A/C compressor, power steering, or even a really bad serpentine belt. The only way to be sure is to remove the s-belt and spin-check the pulleys and listen for squeaks or grinding bearings.

Misalignment of the belt, incorrect belt, worn or loose tensioner, Too tight of an adjustment (many service centers do this on purpose so when the belt breaks in it becomes properly adjusted, I do not believe in this philosophy), The belt is actually one long belt called a serpentine belt.....

If the belt is not tense enough it will squeal, so make sure it's tight enough. Otherwise you can use a stethoscope or long screwdriver up to your ear to isolate the source of the noise.

I have a very loud squealing noise in my 2003 mazda mvp engine when i accelerate. We removed the belts which would eliminate belts as the problem. And that's that it. If anyone has any info please let me know.
Thank you

The serpentine belt area is large. Remove belt and spin the IDLER PULLY of the belt TENSIONER. and listen for a bearing noise. A common failure. Hope this helps

could be your alternator. at start up. alternator usually has a big load because you just use your starter. it would recharge the battery and after a while the battery would be fully charge, the squealing noise will be gone.

check also all the belts if they are individual belts. use some belt dressings to eliminate the noise. sometimes the belt are just worn out and it would also make these noises.

tnx 4 using fixya,

drcool