Before trying to replace an alternator belt, be sure to have the routing diagram and the correct replacement belt. There are a couple different types of alternator belts used in today's engines, and each employs specific replacement procedures. Since there are so many cars that use different types of motors, a repair manual for your specific vehicle will be extremely helpful.
No matter what kind of alternator belt is on your car, you should first know that all the belts are driven by the engine crank.
The older style V-belt systems featured three or four belts---sometimes more---that would connect to each other in pairs and then to a specific grooved position on the crank. The pulleys had to run offset from each other in order to allow room for each other.
Many alternator V-belt applications featured a manual tensioner, usually an adjusting bolt that you would loosen to relieve tension on the belt. Manual tensioners also usually employ an idler pulley along the alternator belt that needs to be loosened in order to wobble the belt off the loosened pulley once enough tension is relieved from the adjusting screw. Once you can get the old belt off, remember to compare it with the length of the new one, and then replace it by reversing the procedure. The repair manual will let you know the proper tension to adjust to for the new belt.
A pivoting alternator may feature a V-belt or a serpentine belt. Regardless of which belt is employed along the pulley of the alternator, the removal and replacement of the belt is the same. You must loosen one or more alternator-to-engine mounting bolts (or sometimes an alternator-bracket-to-engine connection is used) and then loosen the adjusting bolt on the pivot bracket. This will allow you to pivot the alternator in one direction and by doing so, release the tension on the belt and allow removal and replacement.
Serpentine belts became much more popular in the mid-to-late 1980s. This single-belt system snakes around every pulley in the engine, employing an onset alignment. When a vehicle features a single serpentine belt system, an automatic belt tensioner is present. This tensioner uses a coil-spring device to automatically apply the correct tension to the belt. It will pivot slightly in one direction---usually with the aid of a special tool or wrench---and let you slide the belt off the alternator pulley or the most accessible pulley. Once the belt is off one pulley, gently allow the tensioner to sit back in its original position, and then remove the belt from all the other pulleys.
Be warned that not all serpentine belts and automatic belt tensioners are easy to access. A repair manual will give you the knowledge you need to perform the job correctly. In some applications, other components---like a tire and wheel-well splash shield---need to be removed to obtain access to the tensioner and alternator. Some vehicles that employ serpentine belts require a motor mount disconnection to remove and replace the belt. Although rare, it's best to be prepared before attempting.
