Alternator and battery questions 2014 Tahoe LT

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iboughtatahoe23

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Intermittent chirp I’ve always had that I think comes from the alternator, it’s not to loud. I just changed idler pulley, so I don’t think it is that.

My battery voltage is always eratic, it’s always different when I start the truck, but the voltage will stay between 13.4 and 15.2…
Valvoline said my alternator was fine but my battery could be changed. I refused as I was not having any major issues such as starting the car and staying started.

However, in the winter I believe I noticed my headlights would dim for a split second when changing gears from park and vise versa, or using the windows. Also seems my interior lights are getting dimmer? Like a power draw? ( which could be normal maybe?) or maybe I do need a new battery/alternator?
 

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Wes
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all signs of a weak battery, mine is coming up on 3 years old typical lifespan in hot cali.
 

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Wes
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Will the alternator work harder as battery gets older?
good question, my theory is it works less because these trucks since 2005 or so have a rvc regulated voltage control, it has a sensor that measures the battery state of charge and temperature.
so my theory is when the battery gets weak the state of charge/temp is not right so it says hey im fully charged when actually it is at say 80% so the alternator say's ok im done charging for now.
I had a bad battery or internally weak once and it would pass testing so it was not technically "bad" yet would not hold a full charge but had enough to "pass" I did a lot of testing with the tech2 and found it would stay in economy mode even when commanded to go to full charging mode it was really bizzare I could turn on everything wipers, headlights, hvac, seat heater, hazards, etc and it would still not go into full charging mode. it would show like 12.4v etc and all the draw would make the battery go down to around 11v, normaly this would make the alternator kick up and make 13.4+ but it wouldn't do it.
replaced battery and it started working properly again.
just a theory though completely non scientific based on results I had using the tech2 and monitoring the rvc system.
 
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iboughtatahoe23

iboughtatahoe23

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good question, my theory is it works less because these trucks since 2005 or so have a rvc regulated voltage control, it has a sensor that measures the battery state of charge and temperature.
so my theory is when the battery gets weak the state of charge/temp is not right so it says hey im fully charged when actually it is at say 80% so the alternator say's ok im done charging for now.
I had a bad battery or internally weak once and it would pass testing so it was not technically "bad" yet would not hold a full charge but had enough to "pass" I did a lot of testing with the tech2 and found it would stay in economy mode even when commanded to go to full charging mode it was really bizzare I could turn on everything wipers, headlights, hvac, seat heater, hazards, etc and it would still not go into full charging mode. it would show like 12.4v etc and all the draw would make the battery go down to around 11v, normaly this would make the alternator kick up and make 13.4+ but it wouldn't do it.
replaced battery and it started working properly again.
just a theory though completely non scientific based on results I had using the tech2 and monitoring the rvc system.
That’s impressive… so it’s like a variable voltage depending on the state of the battery essentially? So it doesn’t degrade faster?
 

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Wes
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That’s impressive… so it’s like a variable voltage depending on the state of the battery essentially? So it doesn’t degrade faster?
supposedly it's a fuel economy thing, producing like .1 mpg increase
you know it's like one of those controlled test's where they put it on a circle track at constant speed and measure and then yes this makes a difference, when in all reality the consumer will never see or notice the difference. kind of like mpg ratings on the window sticker, it can be taken with a grain of salt.
 
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iboughtatahoe23

iboughtatahoe23

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supposedly it's a fuel economy thing, producing like .1 mpg increase
you know it's like one of those controlled test's where they put it on a circle track at constant speed and measure and then yes this makes a difference, when in all reality the consumer will never see or notice the difference. kind of like mpg ratings on the window sticker, it can be taken with a grain of salt.
So what do you think of my voltage always being between 13.4v and 15.2v? That seems a bit high for some reason man. You said you were experiencing a draw of sorts. It’s like I’m having the opposite. Like it’s overcharging? Maybe 15.2v isn’t even bad? Idk. It makes me think overcharge just bc the alternator has been chirping a bit, the pulley is a teeny tiny wobbly (not loose!)

-Here’s a video of me showing my alternator pulley in the end of the video
And I will be purchasing a new ACDelco Battery tomorrow. I’m wondering what you think of that pulley. And alternator
 

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Dave
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So what do you think of my voltage always being between 13.4v and 15.2v? That seems a bit high for some reason man. You said you were experiencing a draw of sorts. It’s like I’m having the opposite. Like it’s overcharging? Maybe 15.2v isn’t even bad? Idk. It makes me think overcharge just bc the alternator has been chirping a bit, the pulley is a teeny tiny wobbly (not loose!)

-Here’s a video of me showing my alternator pulley in the end of the video
And I will be purchasing a new ACDelco Battery tomorrow. I’m wondering what you think of that pulley. And alternator
To my eye, the alternator shaft looks bent.
 

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Wes
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it does look like it has a little wobble to it.
as for voltage it can really depend on the battery condition, 13.4v or more is good as far as alternator output
 

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