I noticed the other day when I first got back on the road , the belt just happened to stop in the right place and I saw about an inch long piece of the belt missing with 1 thread tore off. Didn't worry about it because I figured it had been there forever, well today I noticed my belt slightly squealing, I made the mistake of spraying "belt dressing" on it. well an hour and about 20 miles later I looked at the belt again and one thread is tore completely off the whole belt. Now I'm not sure if it has anything to do with it but my a/c also stopped working when I first got my pcm back and I have been trying to turn it on occasionally because it will blow cold for a second and then get warm again. I had a friend watch the compressor when I turned the a/c on and off a few times and he said that the compressor clutch wasnt kicking on. I already went and bought a new belt to put on but I know that I don't need to put it back on until I figure out what tore it up in the first place.Should the a/c compressor pulley spin freely?

 

I just pulled the belt off and the tensioner pulley is spinning freely. Is the alternator and a/c compressor pulley supposed to spin freely? What else could have eaten it up?

 

Misalignment of the crank pulley would do it. When you say "1 thread tore off", do you mean "rib"?

The problem may occur when you cycle the AC periodically. The compressor may not be turning freely.

 

I put a screwdriver to the alternator and put my ear up to it , I could hear the bearings inside making alot of noise, does this mean the alt. is shot

 

Look at all of the ribbed pullies (alternator, A/C, crank) and make sure none of the ribs are dented or damaged. That will eat up belts quite quickly.

 

alternator tested good but the battery tested bad. So I still dont know what caused the belt to tear

 

Did you check the pulley alignment and condition, as 2 of us suggested?

Did you watch the A/C clutch while someone cycled the AC, to see if the compressor is seizing?