No idea. The remaining belts looked pretty stringy, so I replaced those as well. Might have been all the time sitting with some animals and heat getting to it? Lots and lots of wasps came with the car, and some other unknown nests as well. It was sitting in a field. When I started it she ran ok and I went out around the block first, then on a five mile loop. When I came back and looked under the hood (after being all proud and showing off my "rescued" car to the family, I saw the flapping belts -one alt and the ac belt.