Check the condition of the accessory drive belts, looking for cracks, delamination, or other signs of wear on the edges of the belts. Check the tension of each belt by pressing the belt with your thumb midway between the pulleys and assessing the amount of deflection.
The normal tension of drive belts must meet the requirements Specifications.
If you notice signs of wear on the drive belts or if they are loose, you should replace the belts or adjust their tension.