Indicative of bad alternator?

[Oaktree]

Wife drives the Tahoe 2022 but last weekend, I get in, drive to Walmart, fill up on gas and it won’t start. Dead battery. I replace the battery, boom, everything works but notice the voltage indicator is low.
Is this indicative of a bad alternator?
Going into the dealer and I need/want to tell them what to look at.
I also have a windshield washer pump that doesn’t work, all fuses are good.

 

[Silverado4x4]

What year Tahoe? Based on the photo it's fairly new..That's normal for a fully charged battery on the lasted gm vehicles as they only charge when the battery needs it "charge on demand ".

 

[Oaktree]

What year Tahoe? Based on the photo it's fairly new..That's normal for a fully charged battery on the lasted gm vehicles as they only charge when the battery needs it "charge on demand ".

2022, ok I remember it being right in the middle of the gauge. I could be wrong or it was a weak battery and always charging, so that makes sense. I’ve been putting a battery tender on it every night until I get to the dealer tomorrow.

 

[StephenPT]

Fire it up and put a multimeter on the battery terminal posts. You should see voltage between 13.5 to 14.5V.

I run a Banks I-Dash on mine and have battery voltage always displayed. I'll see it start out in the upper 13's and then hold in the 14's for most of the drive. On some long road trips I've seen it drop down to ~12.8V, which indicates the alternator stopped charging, but that is normal.

FWIW - the ammeter "needle" is pretty accurate, although there's only 9 and 19 displayed, its position on that bar is sensitive to the actual voltage of the charging system. I'll see it a bit above middle when it's in the 14's and then closer to the middle when it's in the 13's. Only time I've ever seen it display as low as yours is in that picture is when I have the ignition on, but engine off.

 

[Doubeleive]

View attachment 420242
Wife drives the Tahoe 2022 but last weekend, I get in, drive to Walmart, fill up on gas and it won’t start. Dead battery. I replace the battery, boom, everything works but notice the voltage indicator is low.
Is this indicative of a bad alternator?
Going into the dealer and I need/want to tell them what to look at.
I also have a windshield washer pump that doesn’t work, all fuses are good.

even though gm uses a regulated voltage system a good healthy battery should read pretty much 14v all the time, especially a NEW battery, you might see voltage like that while cruising on the highway for a while (economy mode), but not all the time. WHEN YOU FIRST start the vehicle voltage should go over 14v+ more like 15v volt's for the first minute to refresh what was used to start the vehicle.
use a volt meter to confirm at the battery post's as the cluster is not always accurate

 

[swathdiver]

View attachment 420242
Wife drives the Tahoe 2022 but last weekend, I get in, drive to Walmart, fill up on gas and it won’t start. Dead battery. I replace the battery, boom, everything works but notice the voltage indicator is low.
Is this indicative of a bad alternator?
Going into the dealer and I need/want to tell them what to look at.
I also have a windshield washer pump that doesn’t work, all fuses are good.

That is actually an indicator that the battery is fully charged to the computer's satisfaction. When the old battery was dying, the alternator was running near full output to keep it alive.

Look up these terms, Regulated Voltage Control and Electronic Power Management, RVC and EPM. These may be in your owner's manual and they'll be in the GM Upfitter's manuals for your vehicle type. An internet search will at the least provide a generic overview of how the systems work.

 

[Oaktree]

Battery is 12.66 unplugged, with alligator clamps on startup I get zero increase, actually goes to 12.45.

 

[tom3]

That gauge reading along with the dead battery is a real good indication that the charging system is not up to par. Under warranty? Let us know what the dealer does for this.

 

[Oaktree]

That is actually an indicator that the battery is fully charged to the computer's satisfaction. When the old battery was dying, the alternator was running near full output to keep it alive.

Look up these terms, Regulated Voltage Control and Electronic Power Management, RVC and EPM. These may be in your owner's manual and they'll be in the GM Upfitter's manuals for your vehicle type. An internet search will at the least provide a generic overview of how the systems work.

 

[Oaktree]

I think you got it correct. On the drive to the dealer, 40 miles away, I started to se regular voltage readings that I was normal too.
I'm guessing, the battery, which is bigger than stock, and sitting on a battery tender every night, was capable of providing the needs of the car around town. Once on the freeway, it started to draw more juice.

Thanks all for the comments.