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alternator charging fluctuations

J57ltr said:
I'm telling you this is normal for anything past 04+ I have been driving rentals for more years than I care to discuss. I have driven an 05' just like the one I own when it had 5k on it and that one did the same thing. Exactly as the OP described. I have driven cars and watched the voltage stay at 12.5 going down the freeway for hours. I kick on the lights, rr defroster, and AC and the voltage would rise to the mid 13's come to a stop where the fans kick on and it went to 14 and change. This is normal.

If the OP wants to upgrade or make the modification then cool, but telling him there is a problem is incorrect.




Jeff
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Dude i have an 04 comp G. Exactly like his car except a year earlier. Never seen it go to 12.5 while cruising. Not saying i stare at it for hours, but i'll flip through to get back to boost gauge and it looks normal.

But just so you'll believe me, I'll post a log in a day or two. Going on a trip tomorrow, about 2 hours. I'll add battery voltage to my torque log and see what happens.
 


It's something with the regulator\brushes\stator ménage à trois. I'd think atlernator though, because the other 2 last a long time. These alternators have very long brushes, pushing an inch long.
 
Do that, I've literally spent hours driving through nowheresville with only the voltage showing and it's been that way in every GM car I have driven. I first noticed this in 05' and thought it odd. So I would like to see results of your test. I have logged mine and seen the same thing 12.5-14.7.

Jeff
 
I should try a similar log for my 10 seconds and 2.5 second delay regulator, just to see if there is a difference.
 


J57ltr said:
Do that, I've literally spent hours driving through nowheresville with only the voltage showing and it's been that way in every GM car I have driven. I first noticed this in 05' and thought it odd. So I would like to see results of your test. I have logged mine and seen the same thing 12.5-14.7.

Jeff
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Thats what I did, set to voltage and let it fly, you will see the voltage isnt "stable" at all.
 
A voltage booster just sets the voltage regulator to a higher voltage, so it doesn't help stability at all. You can even put a potentiometer on the sense wire, and turn the voltage up if you wanted.
 
The moral of the story is you shouldn't in the first place. Something is wrong with your charging system.
not-sure-if-argument-or-talking-to-a-brick-wall.jpg
 
J57ltr said:
Do that, I've literally spent hours driving through nowheresville with only the voltage showing and it's been that way in every GM car I have driven. I first noticed this in 05' and thought it odd. So I would like to see results of your test. I have logged mine and seen the same thing 12.5-14.7.

Jeff
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see above ^^^^ nothing is wrong with my charging system, go drive
 


You have a 2000. He is talking about 2005+. The only explanation for his experiences are clutches on the alternator pulleys, which you don't have. If you need something to boost your voltage to maintain normal operating voltage, you have something wrong...otherwise you wouldn't need to boost the voltage. You really need to do some research on how electronics work. Like I said, this is basic stuff.
 
I didnt say 12's was my"normal" operating voltage, again your reading into this way to hard.

Hi my name is Corey and I juiced up my voltage for no other reason than because I can.
 
*update*

Alright so i replaced my old stock alternator with a new AC delco one from rockauto. The stock one was about ready to go anyways since after i took it off i noticed the bearing was kinda messed and it did not spin very well.

So i installed the new one last night and drove it around with headlights on, It was at 14.5 the whole time so i thought i fixed it.

Today when i drove it i noticed it did the usual thing where it started at 14.5 and by time the engine is normal operating temp it rests at 12.8.. So is this normal or is there something else i should check/replace?

Also not sure if i mentioned before but the battery is new (1 year old) and before i installed the new alternator i removed the battery and cleaned it with a battery cleaner spray as well as the terminals so there is 0 corrosion.
 


Your good everything is OK. I just spent more than 15 hours logging voltage from a 14 Impala and it does the same thing. My 05' does the same thing. The only time you will see it hold 13.8 is when the lights are on. The reason for this is that the lights are rated for a certain amount of output at a specific voltage and current. You would constantly notice that your lights dimming and brightening if the voltage fluctuated as much as it normally does. If you drive your car you will see the voltage jump from resting voltage of between 12.4-7 depending on condition of the battery. The voltage will go up to between 14.1-8 for a time then it will settle down to 12.7-8 and as low as 12.6. Then after a while it will increase to 13.8 for a while then drop back into the 12's. The PCM controls the alternator and has it put out only what it needs to to charge the battery and whatever excess it needs to keep it at that level. The reason for this is 2 fold, one your not cooking your battery, so it extends the battery life and 2 it cuts down on excess energy wasted running 2 volts higher than it needs to operate the cars electronics.

Jeff
 
J57ltr said:
Your good everything is OK. I just spent more than 15 hours logging voltage from a 14 Impala and it does the same thing. My 05' does the same thing. The only time you will see it hold 13.8 is when the lights are on. The reason for this is that the lights are rated for a certain amount of output at a specific voltage and current. You would constantly notice that your lights dimming and brightening if the voltage fluctuated as much as it normally does. If you drive your car you will see the voltage jump from resting voltage of between 12.4-7 depending on condition of the battery. The voltage will go up to between 14.1-8 for a time then it will settle down to 12.7-8 and as low as 12.6. Then after a while it will increase to 13.8 for a while then drop back into the 12's. The PCM controls the alternator and has it put out only what it needs to to charge the battery and whatever excess it needs to keep it at that level. The reason for this is 2 fold, one your not cooking your battery, so it extends the battery life and 2 it cuts down on excess energy wasted running 2 volts higher than it needs to operate the cars electronics.

Jeff
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Still not a 100% sure about this, but if you've logged that much, i have to default to your data. I looked at my logs a few mins ago that i took earlier while doing some maf tuning. Lowest value i saw was one reading of 13.5. This was over a 30 min or so drive, interstate and city streets. I'm going to take a screenshot of the Ign V sorted lowest to highest and post in a few.

Still, if you've tested it in multiple gm vehicles, and the OP changed his and is having the same voltage drop, this may just be how they're setup. It makes sense.
 
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