Alternator Bearings
Alternator bearings support the rotor shaft inside the alternator. They are a common cause of alternator noise and can often be replaced instead of the complete unit.
What it does
A bearing at each end of the rotor allows it to spin at high speed under belt tension. Heat and continuous high rotational speed make them a wear point.
Signs a alternator bearing is failing
- A whine or growl that follows engine speed
- A rumbling from the alternator that persists with the belt removed and the pulley spun by hand
- Roughness or play felt when turning the pulley by hand
- A squeal that changes with electrical load
When to replace them
Not scheduled. Replaced when noise develops, frequently as a cheaper alternative to a complete alternator.
What to confirm before ordering
Have these ready and the counter can usually confirm the part in under a minute.
- Alternator make and part number, since bearings are specific to the unit
- Front and rear bearing sizes, which usually differ
- Whether the unit uses a one-way clutch pulley that should be checked at the same time
Alternator Bearings questions
Can I replace just the alternator bearing instead of the whole alternator?
Often yes, and it is a fraction of the cost. If the charging output is correct and the noise is mechanical, a bearing replacement is usually the right repair. Bring the alternator details to the counter.
How do I know the noise is the alternator and not the belt?
Remove the belt and spin the alternator pulley by hand. Roughness or rumble points at the bearings. If it spins smoothly and quietly, look at the belt, tensioner or another driven component.