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Charging System Failing

I am in northern MN. I had to jump start my car the other day as it was slow turning over… (Symptom?) tonight when I went out to start it it was pretty dead. I jumped it and the “Charging System” warning and red battery indicator lit up. I noticed that when the car slows the lights and fan go dim/slow. Not sure if the jump start could have done something as well… What do I check and how?

After running the car for 30 minutes the battery was not charging and it was dead. Is there possibly a fuse or relay i could check first?

I would start with a complete charging system test. You don’t mention your car’s model or the age of your battery, but it could be both a bad battery (given how the cold saps the battery) and a bad alternator given the charging system warning lighting up and the battery not charging while the car is running

The first thing I would do, is to remove and clean the battery clamps and the posts with a stiff wire brush.
Then put the battery on a charger over night and get a good charge in the battery. Reconnect the cables and start the engine. If the battery light still comes on you can then drive it to the closest repair shop to have the charging system checked.

One question. When you jumped the battery did you accidently get the cables mixed up and reverse the polarity even for a second. This could short out the charging system and may have burnt out the fusible link that carries the charge from the alternator to the battery.


It is a 2006 Buick Lucerne. The battery is under the back seat and is clean as new. I will charge it in the morning and give it a try.

Is this an original battery? If so, there’s a 99% chance it should be replaced.

You really need a voltmeter to test his. The battery, ignition off, and properly charged, should be at 12.3 volts (very marginal) to 12.7 (new battery) or so. If it is lower than about 12.3, replace the battery.

Start the car, test battery voltage again, it should be 13.5 to 14.7 or so. Anything less and your alternator is bad, or the belt is really slipping - you usually can hear that though.

OK, upon further observation the alternator is whining and smells burnt… So, looks like I should be thankful it’s going to be 30 degrees tomorrow :wink:

Are you quite certain it’s the alternator making the noise, and not the belt?

If the alternator is indeed making noise, it’s got bad bearings, and you should replace it ASAP

you could verify this quickly by removing the belt and spinning the alternator pulley by hand. If it wobbles, or if seems rough when you spin it, the alternator is done for

Does the belt have good tension, and does it look okay, or is it glazed?

Sounds like the stator inside the alternator is shorted, replace the alternator.

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Replaced the alternator and now all is well


I’m glad you’ve fixed the problem

Now, then . . . how old was that battery?

3 years old

I’m guessing the jump start damaged the alternator somehow. Alternator diode or voltage regulator got damaged. This wasn’t one of those tow truck jump starts was it? Sometimes they will beef up the voltage b/c they want to be sure the stalled vehicle actually starts and the owner can drive away without being stranded. After all, that’s the reason to call a tow truck. So they are less concerned that the higher jump start voltage might damage the alternator.

Actually it was one of those new lithium-ion brick sized jump starters

If you wanted to go all scientific like you could take the old alternator apart and check the diodes for shorts & opens. I’d do that, but the other posters here say I have more curiosity than brains sometimes … lol …



There doesn’t seem to be a “curiosity” emoji . . . but this one seems fairly close

$35 core charge vs curiosity… Lol

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