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My Toyota Echo/Vitz/Platz/Yaris alternator is making a chirping sound at idle.

  • It charges just fine at around 14v.
  • It doesn't have a tensioner. (Tension is applied by moving the alternator and tightening the nut on its bracket.)
  • The noise is definitely from the alternator pulley/bearing, not the belt.
  • The sound goes away when the revs increase
  • The sound goes away when I spray a lubricant in the small gap between pulley and alternator housing. (I only did this as a quick method of diagnosing which ancillary was making noise.)

This is my daily driver. Should I treat this chirping noise as the alternator is going to fail imminently and leave me stranded or is it a noise that can be ignored for some weeks or months?

Update July 2017: Car was rear ended at speed and squashed into stationary vehicle in front. Front bar compressed into engine/alternator area. Car is a total loss write off, alternator still works, charging at 14.4v, despite physical damage! :-).

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    It'll probably keep charging until the bearing gets bad enough and seizes, and well, that might leave you stranded, along with a roasted belt to replace. I think your inkling to move this up the priority list of repairs is probably spot on. Fix the things more likely to leave you stranded first.
    – cory
    Oct 27, 2016 at 14:06
  • I think you've found your job for this weekend! Yes - if the bearing is noisy, you should look at changing the alternator.
    – PeteCon
    Oct 27, 2016 at 14:09
  • You could also try to replace the bearing and brushes. Without doubt much more work and risk, but money saving and satisfying when done properly.
    – Martin
    Oct 27, 2016 at 14:35
  • Have you pulled the belt and turned the alternator by hand to ensure this is the issue? Have you used an automotive stethoscope to pinpoint the source of the noise? If the chirp is actually coming from the belt, it will be right at the alternator pulley, which could easily be mistaken for sounding like it's coming from the bearing. Just ensuring you've gotten past all of the basics. It would suck to have you replace a good alternator because a worn out belt is slipping on the pulley.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Oct 27, 2016 at 15:18
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    Update in case anyone is interested: I have a brand new OEM alternator, belt and the associated socket and wrenches needed in the back of my car. For my own interest, I'm going to keep driving until it fails. The noise seems to go away for a while. Its an easy job I can do in 20 minutes at the side of the road so for the purposes of my own entertainment I will keep going and update you when it fails!
    – DizzyFool
    Nov 14, 2016 at 13:18

3 Answers 3

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It will likely get much noisier before it outright fails, but when it does it could stop you in your tracks when it locks the alternator up.

If you have a rebuilder in your area they can replace just the bearing saving you some money. If you are going to go that route I would repair it sooner than later because the bearing may allow the stator and the rotor to come in contact damaging those components and increasing the repair cost.

Also make sure to double check the belt, if any overspray got on the belt when you lubed the bearing it would have caused a belt squeal to go away as well. It wouldn't take much of an overspray at all for that to happen

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If its definitely not the belt it could be a dry bearing or the brushes squealing a little on the commutator.. Take the belt off and spin the alternator manually, as you may be able to gauge the sound source better..
If it is the front bearings & you normally do your own work on the car. Remove the pulley & perhaps try to get some spray grease into the front bearing, it may help make it last a little longer.

If the sound is the brushes and commutator squeaking.. Try to direct some switch/contact cleaner into the rear of the alternator where the commutator is, that may quieten it down.

If the alternator is old though or has seen many many miles, it could just be failing so the only sure way to keep yourself mobile without fear of breakdown is to rebuild or replace it I'm afraid.

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A noisy alternator doesn’t mean the alternator is doomed to fail. Especially if everything is working correctly and there’s no sign of the electrical features of the car not operating effectively. Nowadays a lot of company’s use cheap material to cut back on cost which can also be the cause for some sort of sound being produced. I brought a brand new alternator due to my old one making a grinding sound. The belts and pulleys were also replaced and the sound is exactly the same. Everything on the car works fine. The only issue is a light grinding sound coming from the alternator. Theres no smoke or burning of any kind to assume the bearings are over working or being burnt out. However the alternator is quite hot but Iv looked at different cars and the alternators generally do get quite hot. So my observations tell me that a mere noise with no other underlining factors does not mean the alternator is bad. I think we all are getting very sound protective

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