Advance and AZ say my alternator's fine, I've cleaned/preserved the contacts. Running the heated seats can prompt the Battery and ABS lights to come on, but not quickly and cutting them off solves the problem.
The Battery is new: SLI35AGMDP X2Power Premium AGM Battery for 2017 (hers is an '09-we have the same battery in both cars-mine's the '17) Nissan Maxima V6 3.5L 550CCA Car and Truck.

If I raise the idle, it solves the problem. It's not a crisis level problem now (leave the heated seats off, yeah, I know, or leave my foot on the accelerator) but if it just postpones the inevitable, that's something I'd like to know up front, if possible.

I have a maintainer (I have to find it first), but I've made a point to drive it for over a half-hour and that makes me think that the maintainer isn't the fix. But OTOH, (it's my wife's car and she just retired in November) it's being driven less now than it's ever been driven.

Any help's appreciated. Thanks...

 

Update: I ran my own OBD codes and there is one HVAC code (Fault "1") that won't clear and there were a few that cleared and didn't come back. (HVAC works fine, including the AC, btw.)
None were ignition or battery related. The reader is an Autel MaxiDiag MD805. I don't think it's TOTL, but I didn't buy the cheapest throwaway I could find when I got it about two years ago for my F150.

 

Was the alternator tested at idle but under load?

 

Test voltage at the battery with heater on and off and see what it does.

 

The Wizard & User1: Yes, it was under load. I cut everything on (and off) that I could think of in every combination I could think of and it tested fine at both places.
I put a maintainer on the Battery and it checks 100% charged now. Doing that actually made the problem a bit worse. I have to rev the engine above about 3K RPMs to get the brake/batt lights to extinguish.

Once again, sometimes it seems like it's fine and at others, it goes into what I guess you'd call "fail-safe" mode. If by "fail-safe" you mean "go nowhere fast" mode...

 

So an 09 with how many miles? Does the car have a history? What work has been done to it? Has it ever been wrecked?

 

74K miles. I'm the second owner, bought in 2010. Driven gently, literally BABIED. Regular maintainance only. Oil Changes, Coolant Flush, and a new Battery (aforementioned X2Power) about a year ago.
It's never been wrecked. It's damn peculiar. I finally gave up and took it to a shop, because I don't have the facilities to put it up and check belt tension or voltage drops at the alternator contacts.
I was hoping to avoid that. The dealership wants $$$ just to look at it, so they've priced themselves out of the equation. I have aftermarket audio in the car (installed in 2013) but it's not the problem. It's been meticulously maintained.

 

Aftermarket audio, nuff said.

 

The + post on the alt is easily accessible from the top, ground the meter anywhere.

 

For ****s and giggles, disconnect any aftermarket car audio ampllifiers and see if that resolves the issue. Should be easy enough. I'm still thinking alternator or something related to the alternator or something that could affect the alternator.

 

Nope. I've diagnosed it already and it's not the aftermarket audio. Plus, it was installed in late 2012 and the car ran fine (and charged-and STAYED charged) for nine years. So again...NO...but thanks, anyway. I can see it throwing codes, maybe but the installation itself isn't the problem. I did it myself. It's better/neater/tighter than Nissan's own connectivity. Besides, I'd rather change an alternator once a decade (and it should be obvious that wasn't something I'm keen to do) than listen to Dr. Amar ("1000 midranges can't be wrong!") Bose's assault on the ears of unsuspecting millions...lol...

 

Ok, so what was your diagnosis? I guess I missed that part.

 

You should not be so stubborn to rule out the amplifiers. Although you did a neat install and installed your car audio system 9 years ago, the aftermarket amplifier(s) could be causing these issues....now. Albeit a very small chance IMO, but we gotta rule out everything.

To clarify, when you said the alternator was tested under load, did you turn your on your heated seats as stated in post #1 and watch the voltage? Hopefully you turned on the AC at the highest speed and lowest temperature as part of your load test.
And to clarify post #1 that you've cleaned the contacts, have you wiggled the connector cable that connects to the alternator? Unplug the connector and inspect? Thorough inspection? Quite of few members lately throughout the various generations here on the Org are discovering corroding/rotten connector cables to the alternator, which caused the battery and brake light to come on, which is a dead giveaway that it's an alternator related problem.

Time and time again, I've read people go to there local Auto parts store and get their alternator tested. Tests fine, but weeks later their dash lights up like a Xmas tree. Car is then taken to mechanic who determines it's the alternator. Replacing the alternator fixes the problem.
I suspect your alternator may be starting to die. As it progresses, you'll have more and more issues.

 

I think "The Wizard" nails it. I disconnected the amplifiers early on in the process. (Easy enough to pull the fuses at the battery.) I was coming back to add that I did not replace the head unit, I read that it's possible to do that, but elected not to do it. I hold out a small hope that it's a belt tension issue and specifically asked the mechanic (he's more trustworthy than some, but that supposition is based on the fact that he's waved me off of things like brake pads when I asked if I needed them and he could've just said "yeah") to check the belt tension, B+, and hot connections at the alternator. I should've removed the cowl and took a look myself, but I have health issues (Polycythemia and pretty severe Diabetes Type I) and my skin tears like paper now that I'm not a kid anymore. I had both heated seats and the AC/Defroster engaged, the Stereo up and running (at the AZ and Advance, I disconnected the audio at home noodling with my own DMM), all the lights (on bright) including the halogen fogs. I do appreciate everyone's suggestions. If it was easy, I wouldn't have posted. But I gave my wife this car to drive and unreliability isn't what I've come to expect from Nissans. Except for one disastrous flirtation with an '07 Trailblazer SS (which I sold when I bought the '09), all the cars I've owned are Nissans. Four Maximas ('96-I REALLY miss that car, '04-I really DON'T miss THAT car, '09-pretty good until now, and '17-my favorite of the bunch) and two pickups ('83.5 Dat-San, '89 proto-Frontier, both King Crabs). I've been a Nissan loyalist for a very long time. They seem to be on uneven Corporate ground now, and now that my newest Maxima is out of warranty (except for the drive trains-arguably) I'd really rather not have to wonder if that faith was misplaced. Eleven years with just periodic maintenance is pretty good though. But again, it only has 74K miles on it and stays garaged. Corrosion isn't really a thing with this car, honestly. I know "Rust Never Sleeps" though. It's the price we pay for an O2/N atmosphere, I guess. : - )

 

Hey, don't be dissin my nitrox, my life depends on it. Not sure I saw the answer to my question in that last post though.

 

I forgot to underscore that the alternator shows fine in both scans and at the battery (reading voltages)-UNTIL it DOESN'T. You can hear the idle drop when the Battery/ABS light comes on. I know I'm anthropomorphizing, but it's a little bit "schizoid". It's fine until it's not, and then you know you're on borrowed time until you're off to "limp mode Olympics" accelerator pedal practice. : - )

 

@User1: Sure you did. It's in there, I promise. BTW, if you know what Polycythemia is, then you know I have my own standalone "Turbocharger" when my own O2 levels fall, lol. The Wizard's prognosis is what I've been thinking (while hoping I was wrong) all along. But predisposing folks with my own opinions defeats the purpose of asking for them in the first place. I know what I think already. : - )

 

Ok cool, glad you got it figured out.

 

I diagnose/restore vintage electronics (Silver era Pioneer SX's, RT-s, CT-F's, Marantz, Mac) in my retirement. These aren't Wally World amps, they're pretty high-end/overbuilt by car-audio standards. (Especially the internal PS's...) Everything/anything can break and I know that. Again, I appreciate all of the suggestions. Having fairly high confidence in knowing what it isn't, isn't the same thing as knowing what it is. It's all wire-wrapped/loomed within an inch of its life all the way back. What I was hoping to do was keep it out of the shop. If the alternator's bad, it has to be replaced, regardless. To the degree that I could tell (using an intelligent charger/maintainer that will kick on the instant you open a car door), there isn't very much parasitic draw when the vehicle's off and the audio system has never blown any fuses. It's on the clock now, which isn't the outcome I was hoping for, but it's the outcome I appear to be stuck with...so it doesn't feel like a victory that's for sure. Thanks for the suggestions, everyone...

 

Ok sounds good. Please let us know if we can be of any further assistance, or you resolve the issue definitively. We always like positive outcomes and adding "SOLVED" to thread titles, it helps people searching in the future.