The car alternator brushes wear down over the life of an alternator and may need to be replaced to get the alternator working in optimum condition again
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.
This post shows signs of worn alternator brushes, and how to replace them.
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.
Signs of bad (Worn) Alternator Brushes Symptoms
While these symptoms are not in themselves confirmatory, they can point to bad or worn car alternator brushes:
A Low output voltage from the car alternator, the battery warning light coming on, a sign that the car battery is not being charged properly for a car that’s done over 100,000 miles.
The voltage output from a running car alternator measured across the car battery terminals should be in the range of 13.5-14.5V D.C. A lower voltage may point to worn brushes.
As noted earlier this is not conclusive as it can also be attributed to a loose or weak alternator, battery positive and negative cable connections, or ground or bad battery.
You may also be interested in this post: Why your alternator may be making a rattling sound
How Long Do Alternator Brushes Last
How long the car alternator brushes last depends on the quality of the alternator build and to a certain extent whether is a new OEM alternator or a refurbished alternator.
Some car owners have replaced them at about 170,000 miles mark while others have done 250,000 miles + without replacing them.
If in doubt contact a qualified auto mechanic for assistance.
How to Check Alternator Brushes
Checking whether the car alternator brushes are worn or not often requires that you remove the car alternator from the car.
How long this takes depends on the design and layout of the car engine. In some cars, it can be a straightforward process.
Inspect the car alternator brushes for wear or signs of damage. A worn brush will be shorter in length with the graphite eaten away. Follow the steps to access the alternator brushes.
Always contact a qualified car mechanic for assistance.
Replace the Car Alternator Brushes or Buy a New One?
Yes, alternator brushes can be replaced. They tend to be alternator brand specific so keep this in mind when buying a replacement kit.
OEM replacement brushes 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 the 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.
You may also be interested in this post: Why a car alternator wire becomes hot
Tips to Replace Car 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.
Closing Thoughts
If your car has done over 100,000 miles and has the battery warning light on when driving or low alternator output voltage then it is possible that the car alternator brushes may be worn.
Conduct a visual inspection for wear and damage of the brushes to confirm. 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 the alternator is still charging
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