Ive replaced my AC belt two times now ..keeps getting derailed ..

 

how is the a/c tensioner...spin the tensioner pulley

 

I would just replace that tensioner. It's a cheap part on rockauto.com. I replaced mine just because a couple of days ago. I have a couple of road trips in the next couple of weeks and I thought that the bearing was feeling a shade loose. I think the whole assembly was like $23 bucks. Also, I cranked mine and watched the belt to be sure that it's running true. Also, there is a service bulletin that refers to the tensioner chattering (and failing) due to improper refrigerant pressure in the AC system. Check your refrigerant pressures.

 

I just had my 2001 Suburban's AC belt replaced. The mechanic said that the tensioner was bad and that the pulley was freezing up to a point that the new belt was smoking. He sprayed the pulley and clutch with PBBlaster and freed that up, while I replaced the tensioner myself. So far, so good, and the AC is cold. The old tensioner was so worn that the parts were ready to separate; had that happened the part could have broke loose and broke the nearby transmission cooling lines. At $35 a piece, replace it.

 

That bulletin came with the new AC belt tensioner that I installed. That's a heck of a way to find out there is a problem, after the part fails and you buy a replacement. Tensioner parts could separate and damage nearby trans fluid cooler lines and who knows what else.

 

how should they have notified you?

When a belt fails; you should be checking every pulley while the belts off. When any part fails you should be inspecting for cause.