The belt tensioner on new vehicles is an auto-tension mechanism that automatically applies the correct tension to the serpentine belt. Of course, every vehicle is slightly different in terms of the exact location of the tensioner. But they all work the same in principle. The tensioner slides or rotates clockwise to remove tension and slides counterclockwise to apply tension. The pulley is spring-loaded so that no manual adjustments are ever necessary. Depending on your vehicle, you may or may not need a special key to slide over or into the center of the tension pulley.
Slide the tensioner key over the center slot or nut on the tension pulley.
Slide the break over-bar over the key.
Put the socket wrench over the center nut of the pulley if your pulley does not use a special key.
Turn the tensioner clockwise. You will need to apply a significant amount of force to release the tension being applied by the belt tensioner.
