The alternator belt in my car came off, along with a pulley.
It sounds the the pulley was the source of the problem. Pulleys can cause a belt to come off, but not the other way around. Inspect the belt, it may be ok. The pulley will need to be replaced and the other belts inspected. If you would like this inspected or repaired, consider having an expert mechanic, such as one from YourMechanic, come and diagnose your vehicle.
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