What Signs Show that Car Alternator Brushes are Worn (+Can you Replace them)?

Failing car alternator brushes are probably not talked about as much as bad alternator bearings yet they can fail too over the life of the alternator.

So, what shows that the alternator brushes are worn?

Can they even be replaced or is it even worth it? These are some of the possible questions you might have regarding faulty brushes.

So, in this post, I have compiled some signs that can point to faulty alternator brushes, how you may be able to confirm that they are worn and whether they can be replaced.

Quick answer: There is a good chance that your alternator’s brushes are worn if you have narrowed down the problem with your car’s electrical system to the alternator, ruled out both weak cable connections in the electrical system, a bad battery, and the alternator been in service for several hundred thousand miles.

Note: This is not confirmation – additional inspection will have to be done.

Signs that Car Alternator Brushes are Worn

Thre are several signs that can point to a problem with the car alternator brushes.

Keep in mind, that these signs in themselves are not a confirmation and they may be caused by other faults both within and beyond the alternator.

With all that being said, if your car has done over 100,000 miles and the alternator voltage output is lower than expected or even has no output and bearings run smoothly, battery tests O.K (even on load), and all car electrical system connections are firm then you could have worn alternator brushes.

If the alternator has either a low output voltage or none at all then the battery light will come on, the battery will not charge and if driving the car engine will stop suddenly and the car will lose power.

You may also be interested in this post: Why your alternator may be making a rattling sound

How Long Alternator Brushes Last | How Many Miles?

There is no hard number on mileage when you can expect the brushes to wear out.

In some cases, car owners have reported needing to replace them at about 170,000 miles while others have done 250,000 miles + without replacing them.

How long the brushes last depends on several factors – the quality of the alternator, whether it is a rebuild, an after-market product, or the original issue from the manufacturer.

All these affect how long the alternate brushes last before they can be replaced.

How to Check if Alternator Brushes are Bad

To inspect and check whether the brushes are in good condition, you most probably need to remove the car alternator from the vehicle.

Depending on the design of the engine, this can be an easy or lengthy process that involves removing several parts before you can get to the alternator.

Therefore, consult the service manual or other reputable resources on how you can remove the alternator from the vehicle.

Once removed, inspect the alternator brushes for wear or any breakage.

A worn brush will be shorter in length with the graphite eaten away. Follow the steps to access the alternator brushes.

Can You Replace Alternator Brushes?

Yes, alternator brushes can be replaced. They tend to be alternator brand specific so keep this in mind when buying a replacement kit.

It is likely better to get the OEM replacement brushes.

They will likely last longer and yet do not necessarily cost more than the aftermarket types.

Replacing car alternator brushes can save you some money compared to an alternator rebuild or purchase of a new alternator.

Before you replace them, always inspect the commutator shaft for significant wear.

You may need to seek a qualified opinion on this from a qualified auto tech.

If the brushes have damaged the shaft, you’re probably better off replacing the alternator with a new one.

How to Replace Alternator Brushes

What you need:

  • brush holder assembly complete with alternator brushes,
  • 8mm or 10 mm nut driver or wrench depending on the bolt size;
  • set of screwdrivers to undo any screws that may be holding the cover or brush assembly;
  • alternator manual for the take apart procedure to access the alternator brushes and tools needed

This really depends on the alternator type but the general steps are:

  • Remove the alternator from the car. Then remove the bolts that hold the back cover of the alternator.
  • Swap out the alternator brush holder (complete with brushes) and replace it with the new assembly.
  • Replace the cover and the parts you may have removed when accessing the brushes.

Lastly, fit the alternator back into the engine bay.

Final Thoughts

Signs such as a flashing battery light on the dashboard, the car losing power, or an alternator that is not able to charge the battery after having done over 100,000 miles may point to worn alternator brushes.

However, confirmation that the alternator brushes are worn requires that you visually inspect the brushes for wear and damage.

Replacement kits are usually available and can help you get your alternator working again at a fraction of the cost of a rebuild or a new one.

You may also be interested in the post: Why your battery light is on yet alternator is still charging

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