05 Chevrolet Silverado voltage 12.9 while engine on

[JoeK 10+ year member]

First off, let me say i have nothing installed in this, its 100% stock as of now.

Somebody asked me to do an install and i noticed while driving the voltage was 12.9. When the vehicle starts it goes to 14.4, then after 10-20 seconds it would drop to 12.9 and stay there.

Is this an issue for installing an audio system, or is this an issue in general? It seems odd for 12.9 running voltage. Its stable, just 12.9-12.7

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[kramer_212 10+ year member]

you need a new alternator, and while your at it i would replace the battery with a strong agm such as xs power, kinetik, stinger, batcap. etc...

 

[winkychevelle 10+ year member]

thats pretty much the svcr standalone-voltage-control-regulator its designed to only charge the batts when needed. you can tric it by playing you system right off the back after you crank your truck and the voltage will sit at a constant 15.2 but as soon as you turn it down itll drop to 12.3v. you can have your alt checked but i doubt it's bad.

i used it to my advantage cause my voltage never went below 13v when i used my trick it just had to drop too much when if it was et to 14.4 it would have dropped to 12.5v

 

[JoeK 10+ year member]

thats pretty much the svcr standalone-voltage-control-regulator its designed to only charge the batts when needed. you can tric it by playing you system right off the back after you crank your truck and the voltage will sit at a constant 15.2 but as soon as you turn it down itll drop to 12.3v. you can have your alt checked but i doubt it's bad.
i used it to my advantage cause my voltage never went below 13v when i used my trick it just had to drop too much when if it was et to 14.4 it would have dropped to 12.5v

Sounds right. All lights are bright as hell so i dont think the alt is failing. Even after the 14.4 drop to 12.9 i dont see a difference in brightness

 

[winkychevelle 10+ year member]

Look ar the negative cable coming off the battery if it has a little box attached to it that what it is. If you unplug the box it will cause the alt to charge to 13.8 butit will only charge to 13.8 . This would be fi e but it shortens the life of the alt

 

[akheathen Premium Member]

wish i had the time to map the functions of a delphi plug. yah, sounds like oda functioning, to save gas... not sure if the ecm, or alt needs to see the voltage drop to excite it. if the thing is jumping up there decent without flicker, it's not bad. especially after starting.

 

[MECHMAN 10+ year member]

You could bypass the PCM of the vehicle with an externally regulated alternator. The 2005 and newer GM trucks use a load sensing programmer on the charging wire that goes from the alternator to the battery. If you do not use this item, it could potentially cause electrical issues down the road. Still, when you bypass the factory plug and use an external regulator for the alternator, you will trigger a check battery light. This is common for most newer vehicles and will not have any negative effect on your charging system or engine in general. It's a good way to achieve more consistent voltage and power.

 

[maylar 10+ year member]

What voltmeter are you using? The volts function in my Buick's instrument panel is off a bit.

 

[05fronty 5,000+ posts]

seems like most newer vehicles do this. mine starts at 14.4 and drops to like 13.3-13.5. done that since new

 

[JoeK 10+ year member]

What voltmeter are you using? The volts function in my Buick's instrument panel is off a bit.

Both a dash meter and my cigarette plug stinger meter.

 

[maylar 10+ year member]

Well, the built in meter in my car says 12.9-13.3 which has always annoyed me. Same deal as you, 14+ after starting then it drops. Lights don't dim, so I guess it's normal.

 

[dbjunior 10+ year member]

This is proper charging for a lead acid battery. The problem is agm batts need to be charged at a higher voltage or you can damage them.