There are some vehicle functions we can probably live without. A properly working charging system isn’t one of them.

Among the various common charging system problems you might encounter, one is a noisy alternator.

Here are some common causes of alternator noise.

1. Alternator Belt Problems

An excessively worn or loose alternator belt can produce foreign sounds, as can an alternator belt that is out of alignment.

close up of torn, worn, cracking serpentine belt

Solution: Check the alternator belt for wear or looseness. Excessive material loss may be preventing the belt from fitting the alternator pulleys properly, or the belt may be cracking on either the ribbed side, or on the flat backside.

Replace or tighten as necessary, making sure the belt is properly aligned on the pulley.

Do check the pulley flanges, as bent pulley flanges are a common cause of belts running out of alignment.

Improperly aligned alternator belts will often produce a whining sound. Fixing a misaligned belt may also eliminate the noise.

2. Loose Alternator Bolt

Sometimes, an improperly mounted alternator can produce noises (and battery connection problems) that can lead to failure.

Solution: Often, a loose or missing alternator pivot bolt or adjustment bolt can be the source of the problem. It’s critical to make sure your bolts have a snug, secure fit to keep your charging system operating properly.

3. Failing Alternator Bearings

close up look at alternator bracket on 4.6L s197 ford mustang
(Image/Christopher Campbell)

Failing alternator bearings can produce a persistent whining or grinding noise up to the point of total failure.

There are needle bearings that allow the rotor to spin freely inside the stator. They can break down from excessive dirt and heat. When the bearings fail, the rotor won’t spin efficiently and can eventually seize.

A seized bearing tends to take out your alternator belt with it.

In either case, an alternator that isn’t charging your battery will find you roadside with a non-functioning car sooner or later.

Solution: Replace your failing alternator bearings, or replace the alternator itself.

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Author: Matt Griswold

After a 10-year newspaper journalism career, Matt Griswold spent another decade writing about the automotive aftermarket and motorsports. He was part of the original OnAllCylinders editorial team when it launched in 2012.