Charging system confusion, NEED HELP

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scottg918514

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1.A few weeks ago, had the car running off the battery for about 10 min. Then couldn't start after that.

2. Jumped the battery and then hooked up a charger, charged it to 100%.

3. Tested the charge a few days later and it was 50%.

4. Put a new battery in thinking the battery wasn't accepting charge anymore. Also notice the voltmeter, starting out at 14+ and dropping to 12ish after a few minutes of driving.

5. New battery and voltmeter stayed around 14 for a couple days, then starting dropping to 12 after a few minutes of driving.

6. OK, bad alternator, or voltage reg, which is in the alternator. I replaced alternator, yesterday.

7. Tested battery charge before new alternator, it was 60%. Installed new alternator, drove around, voltage stayed at 14+, tested battery after drive, 90% charge. Yeah, problem fixed.

8. Drove today, voltage dropped to 12ish after a few minutes. @#%&!

9. Tested battery charge, 80%.

What gives????? The cables all look good, clean. Does the voltage regulator drop the voltage to 12 when battery fully charged? (even though it really isn't).

Is there another piece of the charging system that I need to look at?

Also, no codes.
 

08grey

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Yes it does stope charging at some point not sure when. Sounds normal. The old alternator voltage readings are similar to mine. Did you take the old alternator to be tested to see if it was indeed bad?
 

Donnie Yukonie

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Are you running any Real modifications that could be putting excessive Battery Drain? Like say a big sound system / car alarm or other mods?
 
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scottg918514

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Yes it does stope charging at some point not sure when. Sounds normal. The old alternator voltage readings are similar to mine. Did you take the old alternator to be tested to see if it was indeed bad?

No, and it probably wasn't. But, measured charge on the battery and it kept dropping after driving.

I'm not sure how the "logic" works, but it must measure the battery voltage output and when it drops, start regulating the alternator back up to charging voltage, 14+.

New battery and new alternator, probably just needed new battery, since it initially died after only 10 minutes.

---------- Post added at 01:58 PM ---------- Previous post was at 01:58 PM ----------

Are you running any Real modifications that could be putting excessive Battery Drain? Like say a big sound system / car alarm or other mods?


All factory.
 

harveje

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I've been curious about this too, the new systems seem cut in and out to "help fuel mileage" based on ecm inputs. I think the device on the ground wire plays a part in the charging system too. I'd like to understand it more.
 

08grey

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I am assuming this is on your 07. On mine I would find it drawing at different levels at different times. Something as silly as leaving a DVD loaded would have it have the CD player hunt every so often with the truck locked and off. I caught the rear screen coming on also when the radio would hunt. They are weird. A new battery solved all my problems. There is also a common issue with the ground wire. I would google big 3 upgrade and watch the videos and do it if I were you. You will see a difference.
 
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scottg918514

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Freezing weather?

Yes

---------- Post added at 02:33 PM ---------- Previous post was at 02:30 PM ----------

I am assuming this is on your 07. On mine I would find it drawing at different levels at different times. Something as silly as leaving a DVD loaded would have it have the CD player hunt every so often with the truck locked and off. I caught the rear screen coming on also when the radio would hunt. They are weird. A new battery solved all my problems. There is also a common issue with the ground wire. I would google big 3 upgrade and watch the videos and do it if I were you. You will see a difference.

Thx, will check the ground wire just to be sure.
 

08grey

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The electrodes travel on the outside of the strands of the wires so if you see any corrosion or damage that would do it.

Btw a good cup of boiling hot water takes away most corrosion on any battery terminal.
 
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scottg918514

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Tested the ground wire. Used a multimeter to test the battery voltage and grounded to the ground wire end and to the ground, both times I got a reading, so that good, right?
 

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