The Bosch OBD1200 scanner/reader can perform a "charging system monitor" test which gives an indication of alternator health. I used it to help diagnose an issue with a previous car (Acura TL). Just in case you want to DIY and gather more data vs the AG Battery Tracker app...

 

So you were sitting idling in drive with the brake on? That’s interesting. That’s the exact same scenario. At least that confirms that it isn’t my o2 sensor issue that I just resolved.

 

Yep, just idling in Drive with the brake all the way depressed.

 

There's nothing automatic about the parking brake on the IS F. GS F is a whole different story.

Did you note your battery voltage indication when this happened?

My car charges initially at 13.8 vdc, but as soon as it gets to 100% charge, it drops to 13.3. There's a thread about this somewhere here and one of the guys bought an aftermarket piece that plugs into the alternator connection and makes it produce 14.4 vdc.

Getting the alternator out is a PITA without dropping the engine, period. Header or no, it won't make a whit of difference because you have to remove the studs holding the alternator with an E8 Torx socket. No other way to get the thing to drop from where it lives.

Lots of autoparts stores can do in car battery and alternator testing. There are any number of ways an alternator can go bad, not the least of which is having a diode fail in the diode bridge and lose one phase of power entirely. This would be instantly obvious and would not go away. As was said before, Toyotas have just about every light on the dash illuminated when the alternator fails, and nothing but replacing it brings the dash back to normal. AMHIK.

I have nearly 200k miles on my IS F, and I have never observed the problem you describe, but I've never sat for 15 minutes or more with my foot on the brake waiting to move even when leaving a Hawks game and waiting what seems like forever to get out of the parking garage.

IMHO, if there were a problem with the alternator, it would be pretty obvious. You'd be losing battery charge, you'd see AC ripple on the battery terminals (you did take your meter and check for AC voltage on the battery, didn't you? That's a dead giveaway there's an alternator problem.) And the thud sound doesn't seem very likely from the alternator.

Also, the A/C compressor never turns off. Ever. It doesn't have a clutch, it runs whenever the engine is running, and the only thing it does is reduce the volume of refrigerant to near nothing when it isn't needed. We learned all about this way back in 2006 on the original 2IS models.

 

This thread?

 

Multiple days of monitoring shows charging in normal range and battery retention normal. I’m chalking it up to an overload fluke or odd hiccup. I ordered an alternator to be safe, but there is no indication that I need it right now.

 

Unrelated but curious is there any way to just replace the brushes in the alternator? On a 5vzfe swap into a older 4runner I found that while the alternator mounting points were different the electronics were swappable. In addition the brushes themselves were easily swapped as well.

 

27370-58460 is the brush holder part number. It normally comes with brushes installed. At least it did for my Supra (and even at 150k+ miles, the brushes were still hardly worn), so I assume it has them. All the alternator parts are available separately, so you can fix one by getting the individual parts, but often that doesn't make economic sense because the regulator and rectifier assemblies are integrated into the main coil assembly, and that sells for a ridiculous price compared to a rebuilt unit. No doubt the rebuilders are able to get the individual assemblies inside the stator coil and replace them to make rebuilt units pretty cheap.