How Long Can You Drive With A Bad Alternator Bearing?


A faulty car alternator bearing is one of the few problems that can cause alternator failure and inability to recharge the battery. You are already suspecting you have a broken alternator bearing by searching: how long can you drive with a bad alternator bearing?

I will answer that question in this article and explain what your car’s alternator bearing does, why it’s essential, and the tell-tale signs that it’s giving up on you. Most importantly, I’ll explain how to replace a bad alternator bearing.

bad alternator bearing

What is alternator bearing?

The alternator bearing is a small and essential component that allows the rotor to spin smoothly inside the stator. This small component helps the alternator generate the electricity needed to charge the battery and power all the electrical components in a car.

Like other bearings in a car, the alternator bearing can become faulty over time. When that happens, it will not allow the rotor to spin smoothly inside the stator, and it will cause grinding, squeaking, or whining noise when the engine is running. A bad bearing in alternator can lead to failure and inability to charge the battery.

How long can you drive with a bad alternator bearing?

As I said earlier, the alternator is responsible for charging your car battery and supplying electrical power to several electronic and electrical components when the engine is running. If the alternator bearing fails, it will compromise the alternator’s ability to recharge your battery. Leaving the battery to deplete without a means of charging it.

You can drive with bad alternator bearings for 30 to 45 minutes as long as the battery still has power stored to run the engine and other electrical components in the car. However, constantly driving with a bad alternator and relying on the battery will damage the battery. However, the mentioned time is an estimated one.

Symptoms of bad alternator bearing

A high-pitched whine or squeaking noise is the most common sign of a bad alternator bearing. Other common symptoms of bad alternator bearings include slow or unresponsive power windows, dead battery, overheating alternator, difficulty starting your car, loss of power, electrical issues, warning lights, and dimming headlights.

Let’s have a closer look at these signs so you can tell when they are coming due to lousy alternator bearing.

Dimming or flickering headlights

If the road ahead is dimmer than usual, your headlight is likely dim, and it could result from issues with the alternator voltage fluctuations. Plus, your alternator could be the culprit if the headlights are flickering.

In either case, locate a safe place and pull over. Then call your technician to check what’s wrong with the car. If you ignore this sign and continue driving, the vehicle can keep you stranded in the middle of nowhere.

Battery warning light

Another common sign you have issues with the alternator is seeing the battery warning light on the dashboard. This warning light shows something is wrong with your car’s electrical system—the alternator, battery, or both.

Dim interior lights

A faulty alternator bearing will cause dim interior lights. If you suspect the alternator bearing is bad, look at the interior lights. This includes the dome, map, and sun visor mirror lights. If these lights are dim, you may have a defective alternator.

Check your dashboard light settings if these lights are good but the dashboard lights are dim. It could be that you or someone mistakenly turned it down. Sometimes, this is the case after taking your ride to a carwash or mechanic shop.

Dead battery

As I mentioned several times, the alternator charges your car battery. So, it is a simple logic that the alternator is faulty if it fails to charge the car battery.

Rubber burning smell

If the alternator bearing gets bad enough to damage the coils in the alternator or affect the fan belt, you will perceive a rubber-burning smell. However, oil dripping on hot components, worn clutch plates, etc., can cause a rubber-burning smell.

So, if you perceive this smell, do not conclude until you are sure the smell is coming from the alternator.

Random stalling

When the engine is running, the alternator does the heavy lifting on electrical and electronic appliances. The alternator supplies electricity to many electrical components in the car. If it’s not generating electricity, the battery will carry a heavy load without anything sustaining its charge. As a result, the vehicle may stall randomly due to the heavy load.

Initially, the vehicle will start fine because it still has enough power but can’t keep running as you travel several miles.

Electrical and electronic parts acting up

Door windows, power locks, and power seats acting up are other signs of a bad alternator. If your power windows take longer to roll up, know that you have alternator or battery issues. And power seats and locks won’t work the way they used to if the alternator is faulty.

Strange noises

A high-pitched whirring noise is never a good sign. Whining, squeaking, grinding, and slight knocking as the alternator rotates are alternator bearing noises. If you hear these noises while driving or idling the car, increase the RPM and see if the noise will also increase. If it does, you have a faulty alternator bearing or pulley that needs replacement.

How to fix alternator bearing noise?

Here at Vehicle Fixing, we do not only highlight the symptoms and causes of a problem; we also walk you through how to rectify the issues at home. Here are simplified steps on how to fix bad alternator bearing sounds.

Step 1: Remove the battery terminals

Always disconnect the battery before anything else when working on any electrical part. This will help you prevent shorting any electrical component. Locate the negative battery terminal and disconnect it. You can disconnect both terminals if you must remove the battery entirely to access the alternator.

Step 2: Disconnect the fan belts and connectors

A drive belt connects the alternator to the engine pulley and other components. You need to take off this belt before removing the alternator. Locate and bar the belt tensioner to remove the drive belt. After that, unplug the alternator connector.

Step 3: Loosen and remove the alternator

Now, locate and loosen the bolts holding the alternator in place. It is usually three or four bolts, depending on your vehicle. These bolts connect the alternator to the alternator hanger. After removing all the bolts, take a slide bar and remove the alternator from its position. But before doing that, ensure you have loosen all the bolts holding the alternator in place to avoid causing damage.

Step 4: Disassemble the alternator

Take the alternator to a workbench along with the tools you will be working with. Hold the alternator with a vice and loosen the pulley. After that, loosen the bolts and screws holding the front and back covers.

Step 5: Access the bearing

To access the bearing, hit the alternator shaft from the front using a rubber mallet or something that won’t deform the shaft thread. Remember, the alternator has two bearings—one on the front and the other at the rear end of the shaft. Check the damaged one and map it out for replacement. However, I recommend replacing both bearings at the same time.

Step 6: Install the new bearing

With the old bearings out of the way, carefully install the new bearings. When installing the new bearings, do not hit them on the center to prevent damaging them. Instead, press the outer cone until it sits properly in its position.

Step 7: Reinstall the alternator

alternator replacement

Reassemble the alternator by following the reverse order. After that, install it and hook everything else by following the reverse process. Take your time on this. Don’t rush it unless you know your onions. When you are through, give yourself a moment of doubt and recheck everything you did to ensure no mistake.

With everything back in place, put your key in the ignition, start the vehicle and keep running your car for some time.

How much does it cost to replace alternator bearings?

The cost of replacing the alternator bearing ranges between $150 to $300 for both labor and bearing. The price depends on your vehicle make and model—how easy or hard it is to remove and install the alternator and the bearing. Plus, if the serpentine belt is worn and requires replacement, it’ll cost an extra $20 to $40.

Final words

There you go. You can drive with a bad alternator bearing for 30 to 45 minutes or even more as long as the battery has enough power to run the engine and other electrical system components in the car.

If you notice any of the symptoms of alternator bearing going out outlined in this article, replace the bearings by following the repair procedures listed above. Contact your mechanic to take a closer look if you are not the DIYer type.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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