Have you seen this alternator problem before?

This is from my 2009 Kia Sedona with ~140,000m…

I found the brushes in my alternator shorted together with old, waste brush material and a bit of oil or road grime. I’ve never heard of this before and wondered if any of you have had experience with this.

Here’s the story. The Driver’s Door Module stopped working. 2 days later, the traction control light showed that system disabled, the ABS light came and stayed on, the wipers were moving very slowly and the Battery light illuminated. Revving the engine off idle was enough to clear all but the DDM issues.

After charging and testing the battery, voltage drop testing the battery cables, I eventually pulled the alternator. I figured I’d open the cover to the voltage regulator to see if I could spot any problems and discovered the brushes, which live in a plastic cavity, were impacted with the worn brush material that had failed to blow away. I removed the brushes and cleaned everything with brake clean and compressed air, wiped down the contacts on the shaft (is that called the commutator?), reassembled and took it to be tested.

It tested fine - twice. And everything works now.

With a 140,000 miles on the vehicle, I wouldn’t find it unusual.


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At 140, 000 miles, you’ve gotten your money’s worth from that alternator. Replace it even though it’s working now. What caused the failure? Maybe 140,000 miles of usage. Who knows.

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I haven’t replaced an alternator on a vehicle in decades. Last one I replaced was on my 84 GMC S-15 pickup…I think I replaced it around 1989. I’ve easily put more than double (sometimes triple) 140k miles on vehicles and sold them with the OEM alternator and starter.

I would not replace an alternator, but take it to an auto electric shop for repair and testing.

Completely normal wear on a 140,000 mile car’s alternator. I am surprised the brushes were not completely worn away.

Actually, the brushes appeared to have more than 1/2 of their travel left (assuming full spring compression when new)!

in the future I would not use brake clean on electronic parts. try using something like this…


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I used to overhaul my alternators at about 70,000 with brushes, bearings, diode trio, and voltage regulator. The brushes were never significantly worn.

This is basically what happened with the fan blower motor in my Buick. Brushes worn (or whatever the term is for the graphite material in your photo), lots of dust from brush material, blower worked intermittently. I took it apart, cleaned it up, reassembled, and it works fine. Took it to a local shop to source brushes for a rebuild, they kept it about a week, and said they couldn’t find any that were the right size. I stuck it back in the Buick and it works fine, although I’m sure I’ll need another motor eventually since the brushes (or whatever they are) are short and will lose ability to make contact eventually.

The alternator on my 1999 Honda Civic is going strong at 201,000 miles with no maintenance or repairs so far.

Co-worker had the bearings go bad in her Durango’s alternator when she was on a road trip through the southwest, her dad could hear the noise and tell what it was over a cell phone held under the hood but several chain’s threw different parts in that didn’t solve the problem. Dodge dealer in Nevada replaced the alternator and there were no further issues.

Well, the cleaning got me another week of use before it failed again. I disassembled it again and found the copper coating on the rotor output shaft half gone. I have replaced it with a reman from BBB.

Here’s a video of the rotor spinning slowly.

On another discussion but I just replaced mine with a new GM from Rock. I don’t trust remans anymore and prefer Delco. Interesting though that now everyone says to replace it at that mileage but a couple weeks ago said it was silly to pre-emptively replace. Just gotta do what makes sense to you I guess.

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Then again I was planning on keeping my car forever, above and beyond maintenance, then got rear ended.

They’re called slip rings.
Brushed DC motors and “universal” motors (common on older vacuum cleaners) use commutators.
Slip rings are simpler, smoother and last longer than commutators (shown below), if made with good material.

Used to turn them down to clean it up and clean out the slots. Then new brushes, bearings, diode trio, and regulator and away you go again.