Sight, Sound and Smell
These symptoms are grouped together as signals from the senses. They're less definitive than a warning light; however, these signs of alternator trouble can tip off a driver that there's something going on that shouldn't be happening:
- Sight: Mechanics are accustomed to customers complaining of classic alternator issues, and then opening the hood to find the belt missing, hanging off the engine block or so loose it's flapping around the engine compartment. A quick visual check of the belt for cracking, excessive wear and other age issues can give an indication of a future problem. Also, the belt must have the proper tension to run the alternator correctly; too much tension is just as bad as not enough. A quick check of the belt tension is usually enough to determine if a problem exists.
- Sound: Drivers will sometimes complain about hearing a "growling" or "whining" noise before an alternator gives out. The alternator is driven by either an accessory belt or a serpentine belt in conjunction with the crankshaft pulley. The alternator pulley typically spins about two or three times faster than the crankshaft pulley to produce the power necessary at lower engine speeds, such as at idle. The alternator pulley spins on a shaft, which in turn is supported by either bearings or bushings. If the pulley is not in correct alignment with the belt, if it's canted on the shaft or if the bearings and bushing are worn out, the growling or whining noise will let you know there's a problem.
- Smell: The scent of burning rubber or hot wires will often accompany alternator failure. A pulley that isn't in alignment or not turning freely will cause more friction on the belt, which creates heat and then the smell of burning rubber. The hot wire scent can be caused by an overheated alternator, one pushing too much power through the rotor and stator.