Alternator Warning Signs!

[alsalih]

Well guys, it finally happened, my alternator fried on me yesterday (110 K miles on 98 LS400) but I still managed to make it home. There have been many discussions on alternator problems, noises, and failures but I thought I would contribute my experience on this in hope of helping someone out there. The symptoms were a high pitched whine noise consistent with engine speed especially above 1200 RPM which has be ongoing for 9 months. You can also hear it when driving up to 40 mph, beyond that wind/road noise covers it up. The noise will however change in pitch as you slow down and this might initially lead you to believe you have something wrong with a drivetrain component (front wheel bearing) or possibly an air leak from the front right door trim. Yesterday, I noticed that my "D" light for the auto trans was weak and would glow brighter when I moved from a stop (this has always been my battery strength/alternator condition indicator on previous cars). Anyway, I have this real cheap but very useful battery/alternator checking device that plugs into the cigarette lighter and it has always indicated that the alternator was putting out the correct charge, until yesterday when it indicated a low or inadequate charge from the alternator. This handy plug in tool saved me the headache of having to remove the alternator and taking it to a shop to have them check it for me under load as I can duplicate this from inside the car. This is a real bummer and surprise for me as my alternator on my 93 GS300 had lasted 213K miles before it failed. I should mention that I don't have and have not had a power steering leak on this vehicle. Remember, alternators can fail by simply not outputting enough charge!

[wwest]

Were I you I would replace the slip ring brushes in the alternator before replacing the alternator itself.

When the alternator failed on my 92 LS the first indication was miscellanious and intermittent diagnostic lights on the panel. I changed out the battery and those symptoms went away until the new battery's charge level declined.

It turned out that the PS leak had nothing to do with the alternator failure, the slip rings on the alternator shaft were worn down to the steel shaft. The slip ring brushes were still very serviceable.

[alsalih]

Actually I was very close to going out and buying the two bearings and new brushes which the dealer had, however, I was not getting Christmas lights in the display, the normal lights were on however they were weaker. That combined with the bearing noise made me decide to just replace it.

[akewlguy]

Although the LS has a steller maintenance record... Mechanical and electrical parts will be mechanical and electrical parts. Each one is different and there is no telling when they will fail. Of course pounding the hell out of a car could effect mechanical more then taking it easy..

[alsalih]

Well after doing some more research I have finally pinned down what really caused the failure. The high pitched whine noise is not the alternator bearings, it's the faulty rectifier (diode). I didn't know this but a faulty rectifier (or one going bad) will produce a whine noise and will eventually fail. A faulty rectifier will cause the reduced output as I had noticed.

[prix]

so is this (rectifier) a component of the alternator?

Well after doing some more research I have finally pinned down what really caused the failure. The high pitched whine noise is not the alternator bearings, it's the faulty rectifier (diode). I didn't know this but a faulty rectifier (or one going bad) will produce a whine noise and will eventually fail. A faulty rectifier will cause the reduced output as I had noticed.

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[alsalih]

Yes, this a component internal to the alternator.