Bad alternator?

So the other day I noticed that the battery gauge was moving around at idle.
I didn't think much of it until I left town and suddenly everything was flickering in the cab and i was losing power.
I stopped by O'reilly so they could check the battery.
They find that the alternator and starter are OK, but the battery is on its way out.
No big deal, I get a new one and am on my way.
The battery gauge settles back to its usual spot and everything is great again.
When I start it again the next day, everything is still working until I start driving and notice that the odometer display is flickering a little. The battery gauge is also randomly moving up and down within a couple volts. I turn on the dome light which also flickers.
I stop by O'reilly once again. They don't have the same meter they used the first time but can check voltage on both the battery and the alternator. Battery is fine but alternator seems to be putting out a little over 12V.
I look up how to replace the alternator and as you may know, it is no easy work.
So I dropped it off at my mechanic for an alternator replacement.
He calls me the next day asking why I need to replace the alternator. I tell him everything that has happened and then he tells me that he just tested everything and it's all working just fine, which is super confusing.

So my question is.. does the alternator really need replacing or should I be chasing a different issue?
My guess is that it's on its way out and may be functioning enough to be okay one moment and problematic the next.

Thanks for your input!

 

Sounds like a loose connection / ground. Tundra alternator usually puts out 13-13.5v.

 

The alternator voltage is a little low but I don't think that being a bit over 12v would cause flickering. Even if the alternator voltage dropped below 12, the battery should lift the voltage up. (I'm not an expert, that's just my understanding).

So I'm with AZBoatHauler... Sounds like a loose connection. That would also explain why everything tests fine when parked-perhaps vibrations from driving are shaking the connection loose.

 

Got it. So maybe loose connection at the alternator?

 

I had an alternator fail symptoms started with the headlights getting dimmer and the battery gauge reading low about a month later the alternator completely failed when I was on the freeway close to home the dash flickered just before failure. I would say you have a loose wire somewhere

 

I have also read that a worn out serpentine belt could have trouble engaging the alternator pulley.

 

What year Tundra and how many miles? These are important to help diagnose issues like these.

Dan

 

2010, 152k miles

 

If the belt and tensioner haven’t been done, it’s certainly time. Idler pulley too.

 

Drove my truck again today and on the way home the battery gauge needle started moving around erratically again, slowly going down in voltage as well. Dome lights and dash flickering.
The mechanic had his tester show 13.79V for the alternator. So my guess is that it is no longer charging properly.
Going to install the new alternator tomorrow and see if it fixes it.

 

Bench test the alternator

 

Ended up replacing the alternator. What an awful job.
It took me about 12 hours from start to finish.
Having the tow package means extra hard lines right under the alternator, making removing some of the bolts nearly impossible.
Symptoms are gone so far. Even when things seemed okay, the battery gauge would flinch for a second while turning on the headlights. No more.

 

Great work @Mbril thanks for sharing, and keep us posted. I dread the day I have to do the alternator on this thing. I’m sure there’s a good reason, but I don’t understand why Toyota placed the alternator on the bottom on both the 4.7 and 5.7 V8’s.

I’ve done the alternator 3 times on 4.7 motors, but this one appears to be on another level of PITA.