Serpentine belts and engine pulleys are responsible for using the power your engine produces, to utilize different systems in your vehicle. Is your car making ear wrenching squeals? Your serpentine belt can very well be the issue. You may have one belt, or two belts depending on the vehicle. Both possibilities are responsible for powering your air conditioning, power steering (If not electric power steering), alternator, and water pump. A bad belt can result in no A/C, loss of power steering, dead batteries/non-functional electrical systems, and overheating. Their respective pulleys can also be a cause to these issues. All repairs are priced as such; Price of part, plus installation fee, plus old part recycling, plus trip charge.