Here Are Some Warning Signs of a Bad Alternator


alternatorYour car’s alternator is the heart of your car’s electrical system. Therefore, a faulty alternator can leave you stranded. Being proactive about your car’s maintenance issues is the best way to keep from being stranded and avoid costly repairs.



So, here are some warning signs of a bad alternator.  Since the alternator provides electrical power to recharge the starting battery, a low or dead battery maybe a sign of a bad alternator.  If your car fails to start or all you hear are clicking noises, that means your battery is dead.

That may or may not indicate a bad alternator.  More testing would be needed.  You have to eliminate the battery as a possible cause of the starting issue.

You can either replace the battery, or [easyazon_link asin=”B00D42AFS8″ locale=”US” new_window=”yes” tag=”carbattery0e-20″ add_to_cart=”yes” cloaking=”yes” localization=”yes” nofollow=”no” popups=”yes”]jump start the car and see if the battery will stay recharged. [/easyazon_link]If the alternator is working properly your battery will be charged up after running the engine, and your car should start up normally.


If after replacing your battery you still find the battery low or dead after several days there is an issue with the vehicle’s recharging system. Check the following first.



Alternator test


A Simple Test

If you do not find anything obvious check the voltage at the battery with a volt meter. With the engine running you should have 13 to 15 volts as you can see in this photo.  Anything below 12 volts is indicating a bad alternator.

warning signs of a bad alternator


Other Signs of a Bad Alternator

As I mentioned before, the state of battery charge is the main clue that an alternator maybe bad. Some other signs of a bad alternator would be less obvious.

It’s important to note that alternator problems can also be battery problems. So it’s important to test or replace the battery first.

Warning Light

The most obvious sign of a bad alternator is the warning light in the instrument panel. If there is a red light illuminated there, check to see if it’s the charging system fault light. The check engine light, or service engine light may also be on.

Dim Headlights

Another clue is dim headlights. Check to see if while accelerating the engine the lights get brighter. If they don’t you may have an alternator issue.

If they do get brighter, the problem is most likely the battery. The battery has a huge role to play in your car’s electrical system too.  Along with dim headlamps you may notice other interior lamps dim.

Engine Power

You may also notice a lack of power from the engine and or the engine running rough.  This is because in the event of an alternator failure there would be a lack of electric power to support the engine’s ignition system and fuel system.


Wrap up

Those are the main signs of a bad alternator. Again, you have to determine if the cars battery is not the problem before you suspect any alternator issues. Most of the time it is the battery.

Many auto parts stores will check your charging system for free. It is a very simple check with a volt meter.

So to recap, the main sign is the battery not staying charged. You will also get a warning light in the instrument panel.  Then slow or complete failure of the electrical system.

I hope you found this article on warning signs of a bad alternator helpful. Please leave a comment or question below.


Thanks For Visiting!

Edward Verheyden

Edward Verheyden is the founder of  He has a 30+ year mechanical background and is the main reviewer here.  He lives in San Diego CA with is wife and two daughters.


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