14+ when I start my truck but after I drive for a while it drops to about 13 volts

2005 CHEVROLET SILVERADO

180,000 MILES • 6.0L • V8 • 4WD • AUTOMATIC

ZOEY'SDAD

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My voltage on the dash is 14+ when I start my truck but after I drive for a while it drops to about 13 volts. It used to stay at about 14 all the time. I changed my alternator and it still does the same thing I put a volt meter on the battery to check the gauge and it is correct. If I shut it off for a few minutes and restart it it goes up to over 14 as it always did and then drops again after a while. I did have the auto parts store hook up their hand held tester and it didn't show a problem but it wasn't an old school load tester so I don't know how accurate theirs is. Will a bad battery show this symptom?
Thank you

Aug 21, 2019 at 1:33 PM

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KASEKENNY

AUTOMOTIVE REPAIR CONTRIBUTOR
18,907 POSTS

Couple questions. First is there any issue with the battery or charging system that causes the battery to drain?

What I would suggest is having the alternator tested using this guide.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Most parts stores can do this, but this is different than checking for codes which is what it sounds like they did. If there are no codes, then we need to start suspecting that this is normal.

Take a look at the entire system description below. Once the vehicle is warmed up and the load does not demand a higher voltage then it will drop the voltage output down to just below 13 and a half volts.

Plus, there are many different operation modes where it will be down to 13 volts as well.

Please run through all this info and let us know if there are any issues. If there are not, then I would not worry about this but let's start with this and go from there. Thanks

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Nov 5, 2021 at 1:37 PM