Bad alternator?

[bdbull]

Think I might have a bad alternator on my wife's 2015 Tahoe.

Had a slight whining noise show up about a week ago. I couldn't find anything right off the bat and it didn't affect the drivability so I was gonna wait until this weekend to troubleshoot further. Today she sends me a picture of a "Battery Saver Active" message on the DIC with the batter gauge at the low marker of the normal range. When she got home, I went out and did some preliminary tests with my multimeter. Just testing the battery with the car off, it's right at 12V. Cranking the car up and then testing (which I've never done before but ChrisFix recommends) the voltage was below 12, around 11.2. According to his video, that indicates a bad alternator. I can get an alternator from Amazon delivered on Sunday, or I can pay twice as much and get one from the local auto store tomorrow. Can I wait it out or is this something that will leave her on the side of the road? The message didn't show up when I had it running so I'm hoping it's just slowly on it's way out and not completely dead.

ChrisFix video:

 

[TXt3rr0r]

It will likely leave her stranded, the battery alone will not provide the engine with the correct voltage long enough to get very far, I'd say park it until it's fixed unless you want more headaches

 

[bdbull]

It will likely leave her stranded, the battery alone will not provide the engine with the correct voltage long enough to get very far, I'd say park it until it's fixed unless you want more headaches

That's what I'm afraid of. From where she took the picture today, she drove 35 minutes home with it like that today. Perfect timing for us, when everybody has somewhere to be at the same time.

 

[tom3]

If you have a battery charger and the battery is in good shape you could probably get by for a couple days with short trips. I probably wouldn't chance it.

 

[TXt3rr0r]

That's what I'm afraid of. From where she took the picture today, she drove 35 minutes home with it like that today. Perfect timing for us, when everybody has somewhere to be at the same time.

That's how it always happens right???? If it wasn't for bad luck, we wouldn't have any at all!

 

[bdbull]

Think I should replace the serpentine belt while I'm in there? Truck has 204k miles on it, and as far as I can tell it's never been done. I know I've never done it and we've owned it since 50k.

 

[Geotrash]

Think I should replace the serpentine belt while I'm in there? Truck has 204k miles on it, and as far as I can tell it's never been done. I know I've never done it and we've owned it since 50k.

Yes. Absolutely replace the belt and I would also replace the tensioner and idler pulleys.

 

[bdbull]

Yes. Absolutely replace the belt and I would also replace the tensioner and idler pulleys.

Any idea on part numbers? I think the tensioner is 12670574, but I can't seem to find a Tahoe specific part number for the idler pulley. Is it a generic part?

Edit: Is it one unit that contains both parts?

 

[Tahoe14]

Did you try Rockauto and there is a discount code. Usually fairly easy to look up parts.

 

[bdbull]

Did you try Rockauto and there is a discount code. Usually fairly easy to look up parts.

Yeah that's what I usually use to lookup parts. There is no specific idler pulley for the Tahoe, and a search for idler pulley returns generic results. That's why I'm wondering if the part listed as the tensioner is actually both. I don't know enough about the parts to know. I just watch YouTube videos and do what they say.

 

[Geotrash]

Any idea on part numbers? I think the tensioner is 12670574, but I can't seem to find a Tahoe specific part number for the idler pulley. Is it a generic part?

Edit: Is it one unit that contains both parts?

Idler pulley is: https://www.rockauto.com/en/catalog...,5.3l+v8,1433400,belt+drive,idler+pulley,6956

 

[17 Yukon Denali]

Alternator/ Belt/ Tensioner. These alternators have been known to seize up so hard that people mistake it for a seized engine because they can’t turn the engine by hand.

 

[adriver]

That video doesn't apply to you. The old style alternators used internal voltage regulators. The alt would constantly run, and would aim for a desired voltage (14.4v), then shunt the overage to not overcharge. Starting in 05, the alts had external voltage regulators, and are controlled by the BCM. The alternator is designed to fluctuate, and be ran at lower voltage. Instead of always running, it is designed to run when there is a need for more voltage. It does this to improve mpg. There is a short mention about it in the owner's manual. What you listed is within spec, and doing exactly what it's designed to do. Nothing you have said so far is a problem with the alt, (without knowing where the noise is coming from).

 

[bdbull]

Update on this...

Had to run a little longer on the bad alternator because I ordered the wrong part the first time. Wife drove home on Monday and got a message that she had no power steering. I read that the power steering on these things are electronic so that made sense to me. Got the correct alternator in yesterday and put it in. Had some trouble putting it in as it was a little wider than the mount it was going in so I had to sand it down a little to get it to fit. Hooked it up and it's been good so far. Battery gauge in the truck jumped right back up to the middle when I cranked it. Will continue to monitor, but I'm hoping this is behind us now.