I have a 2011 sr5 with 288k miles and last week the battery light started flickering intermittently. Checked and cleaned all connections I know to check. Belt seems fine Battery is fairly new and alternator is original. Dealership claimed battery and alternator tested fine (but could not get warning light to flicker or illuminate) and a few days later audio started skipping and headlights weakening and rpm’s sort of going haywire at times. Alt tested low at advanced.
Decided to replace alternator yesterday. Got the higher output carquest (I know that could be my issue now.)
Drove it quite a bit today (about 50 miles) and everything seemed great until went to leave the house again this evening. Battery light is now illuminating (very dimly) with no other issues. Drove about 30 miles like that and no symptoms outside of the light. Alt tested 13.2 at advanced. I know that’s low.
Do I just have a crappy new alternator and need to get an oem/denso? Also I broke the plastic cover for the wire that goes from batter to alternator (the one with 10mm nut) and wrapped in electrical tape. Can’t imagine that’s the issue but maybe worth noting.

Did you return your original alternator? If not, pull the brushes out and have a look. If you did, it wouldn't hurt to look at the brushes in the 'new' one. To me, this sounds like worn alternator brushes, which are $15-$20 and very easy to replace.

Sort of what I was thinking. Still have the old one. If that works hope I can get the money back on the new one. Thanks.

Good that you kept it. If you haven't done it before, there are several videos on replacing brushes. If you already have the alternator in hand, it's literally 5-10 minutes.

Since you've noticed some funky stuff with the RPM and your headlights, it might be a good idea to dig a bit deeper. Check the ground connections, both on the alternator and throughout the electrical system. A weak ground can cause some weird behavior.

Also, take another look at the serpentine belt tension. Even if it seems okay, double-checking won't hurt. Any slip or play can mess with how well the charging system works.

Now, about those RPM issues – give the throttle body and its sensors a look. Sometimes, problems there can mess with the engine speed, and that can mess with the charging system indirectly.

And, keep an eye on the battery voltage in different situations – when you're idling, accelerating, and when you've got accessories running. This can give you some extra clues about what's going on with the charging system.

Thanks a lot. I read another thread where someone rebuilt the alternator but the light remained on for a week or so while it was sort of breaking in. It said “
maybe its me and my rig. I did new Toyota brushes and after install the voltage was at 12.9. I thought ....ok...I screwed up...but I had no time to play again, so I figured Id let it ride till next week and pull it apart again.
after a few days voltage was back in specs. so maybe they need time to conform to the round rotor since new brushes are flat
rounded off after a few miles fit the contact surface better“

Since my replacement is a rebuild is it possible they just need a “bedding in” period?

Also my display in 2011 doesn’t have a voltage meter. Annoying they stopped putting this on the dash.