drive belt shredding!

i've had 2 drive belts shred on me in the past week or so. i'm looking for info on why its doing this and how to fix it

Welcome to AF!!

There are two common reasons that a belt will shred. First, there is damage to one of the pulleys on the accessories that causes the belt to shred or it is out of alignment that is causing the grooves to be misaligned and the belt gets cut and then shreds. You will need to check all the pulleys and the tensioner to see if they all have free movement and that they are smooth. Also make sure one hasn't locked up as that may be causing the belt to overheat and come apart.

It could also be the wrong belt...

I bet it is more likely you have some sort of debris on the pulleys that is tearing it up. Make sure all the grooves are clean and nothing is stuck between them.

Check the crank pulley to be sure that it isn't out of alignment. The crank pulleys on Escorts have a habit of separating from the harmonic balancer (timing ring).

I had an 88 Mazda 323 before that did the same thing. Turned out to be a defective alternator (apparently a big problem Mazda failed to acknowledge). Well anyway 4 belts, and 3 alternators later I finally got it fixed, what you should do is find someone with a laser temp reader, its a unit that you point at things to read the surface temp, and check you pully temps. Thats how I cured my problem. Its not too often the grooves the get dirty enough to shred belts, I have been under cars for 22years and never seen it personally that is *shrugs*. Good luck!

ok here's what i've found so far. harmonic balancer is fine. tensioner is fine. all the pulleys have free movement. put a new belt on and made sure to line all grooves up. cranked car and the belt came up out of one groove on the alternator pulley. i've recently changed the alternator. i got a rebuilt one. could it have the wrong pulley on it? even when i fixed the belt back into all the grooves as soon as i cranked it the belt came back out again.

Its just as I said.. Alternator is bad. Get it out of there and get another one!! I had to prove to the parts store the pulley was heating up and guess how I did it? With a laser temp sensor, I suggest you go find one!!

Or if the alternator spins well, doesnt have any play in the bearings or any binding as it turns - could they have put the pulley on wrong? Such as without a spacer washer between it and the bearing the pulley is drawn down onto? Or the pulley put on backwards? Those pulleys arent hard to remove, if you have an impact wrench to use on the nut. Even an electric impact wrench will work fine. You can hold the alternator in one hand, the impact wrench in the other - to get the nut loose and to retighten it later.
On another car I had the problem of short belt life - which turned out to be an alternator pulley that had been slightly smashed on its outer side at one point, and hammered back -almost- to the right width.
Of course the alt. pulley has to have the same number of 'grooves' as does the crankshaft pulley.

Use a straight edge and check for proper alignment. As some pulleys are thicker put the straight edge on one and go to the alternator. Use a small rule and measure to the edge of the belt on each pulley. It will probably stick out when you check this way. Check all pulleys the belt runs on. You may have left a washer used as a shim or the pulley could be wrong as suggested.
I have had a mount crack and put stress on the idler so the pulley ran in the middle of the belt. It would cut a belt in a days time.
Watch from the side of the fender you should be able to see what is happening.