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Discussion Starter · #1 ·
I have a 2011 sonata limited while driving home all the lights started blinking and car wanted to turn off. I got home and it died. I had a friend come give me a jump and it started right up. When I took jumper cables off the instructment panel light went out everything but the car kept running.I turned the car off after a while and could not start it back up. I jumped it again to start and after it started I took the negative ternminal off to see if it would still run. It didn't it died right away. Did the jump again started right up. Took the positive terminal off died right away. I thinking bad alternator what do you think? Battery was tested and everything was ok. Need help please
 

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First off...


1. Don't disconnect the battery while the engine is running. The battery acts to filter out possible spikes from the alternator. This is especially important if the alternator has a fault. You could do lots of damage to the electronics in the car. This trick of disconnecting the battery worked okay in the 70s before all the electronics, but isn't so good now. My father did damage to a couple of modules on his late 80s car when he tried it.


2. Always disconnect the negative battery terminal first, never just the positive terminal. The reason is that all the metal in the car is connected to the negative terminal (if you haven't removed it). If you slip at all with your wrench on the positive terminal and it contacts metal on the car/engine while still on the positive terminal, you will have a massive short. The hundreds of amps flowing through that wrench could vaporize it and leave you with major burns. It's even worse if the battery is venting hydrogen and you ignite it.


After that...
It does sound like you charging system has failed. Often, but not always, the alternator is at fault. There are simple tests that you can do with a multi-meter to determine for certain. There is no reason to guess and throw parts at it.
 

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Additionally, you can pull up to an autozone or another like shop and they offer free battery and alternator testing if you do not feel up to it or have the equipment/skill to do so properly.
 

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Discussion Starter · #4 ·
thanks for the reply....i stopped by autozone had both tested they said the alternator tested good but the battery needed to be replaced. brought a new battery had alternator tested at another autozone and they too said it was good. i guess i'll put the alternator back in and hope for the best. even at autozone they said that removing the positive terminal from battery should keep the car running on the alternator. thanks again.
 

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If the alternator by itself tests good, but it's not charging the battery, then it's time to look for other charging system faults. Check the power connection to the alternator, and the control connection(s) to the alternator. The ground between the engine and the car and the battery is probably good, since the starter is working correctly, but I'd check that too.
 

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i guess i'll put the alternator back in and hope for the best.
Put the alternator back in?

Did you remove it and have it bench tested? That's never a good idea. It's better to have it tested on the car. That way the whole charging system is getting tested. The alternator itself might be OK but there could be a problem elsewhere in the system. What you describe certainly sounds to me more like a charging system fault than a problem with the battery.

Have you checked there's voltage on both ends of the main ALT fuse at the battery?
 

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Put a meter on the battery terminals with car off. Should read roughly 12.xx volts DC. Start car, turn on all accessories (A/C, fan high, headlights) have someone step on gas pedal and try to keep RPM's around 2000, put the meter back on and you should read roughly 13.5 or higher.
 

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Put a meter on the battery terminals with car off. Should read roughly 12.xx volts DC. Start car, turn on all accessories (A/C, fan high, headlights) have someone step on gas pedal and try to keep RPM's around 2000, put the meter back on and you should read roughly 13.5 or higher.
Idle voltage is common to see 14.2 - 14.4 volts,, add couple loads, see what you got..

BTW,, Hyundai seems to think paint is good thing between load carry lugs,,

But as we should all know,, "Paint is an insulator,, NOT a conductor"..
 

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Idle voltage is common to see 14.2 - 14.4 volts,, add couple loads, see what you got..



BTW,, Hyundai seems to think paint is good thing between load carry lugs,,



But as we should all know,, "Paint is an insulator,, NOT a conductor"..


Yup so clean off all those terminals and lugs you can locate. Remember you aren’t concerned with the top but rather the bottom , the bolt threads and mating surface. I always put dome grease on the mating surfaces and threads to assure good grounding.
One other thing. If you ever do end up getting a new alternator KEEP THE OLD ONE. The rebuilds you buy at stores may well almost but not quite worn out themselves. Such is the world of definitions in the rebuilding industry.
Take it to the local DC motor rebuild shop or and have them go through it. Then it will be right. Cheaper too. I’ve been doing this for decades and never paid over $65. There’s not much to those things, the body’s last nearly forever and the internal parts are actually cheap.


Sent from my iPad using Tapatalk
 
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