Last night, we got stuck waiting on a very big train. We sat there for probably 15 minutes.

I heard and felt a light thud while idling with my brakes on, in drive.

I got a Christmas tree of lights on the dash. Stability control, traction control, check engine, and parking brake.

I pulled my code scanner out on my phone… and had zero cell or fault codes. Weird.

When I finally hit the gas, all the lights went away and car was fine.

Can this car apply it’s own parking brake if it decides you’ve been idling in drive for too long?

A car should never have that much of a sense of humor.

 

Sounds like the alternator. How old is your battery?

 

Why do you say so? Maybe a year. It’s a lifePO4 battery.

 

Bad alts often throw all the Christmas lights you're talking about. The fact that you heard a sound & the lights went away once you applied the throttle (spinning up the belt) makes me think it's the alt. Had you not heard a sound, I'd point the finger at the battery first which is still a possibility. Check the terminals as well & make sure they're tight - I know you were in your car recently doing other repairs.

ISFs are incredibly power sensitive and act real weird with bad alts, weak batteries, bad components, etc. Once, I had a bad aftermarket LED light in the overhead dome light that was making the gas gauge act like a VU meter and I swear was impacting the shifts in the car. The tipoff that this was the problem was blind luck - I had the door open troubleshooting electrical which had the LED on for an extended period & created a burning smell. Another time I didn't secure the negative terminal correctly after some work I was doing and the head unit went haywire while I was driving.

 

I had my fog lights on for the first time, I think ever, last night. So it was pulling more power than usual.

I’ll check the battery cables. I have a tracker on the battery and it stays around 99-100% charged. I get a message every time I walk by the car with the battery status.

That’s not great timing because I have a track day (drag strip) and cruise this weekend 2 hours away.

It ran fine this morning. Do alternators slowly go out, or should I expect to be stranded this weekend? If so, I’ll try to get it replaced asap. I’d prefer not because I’m wildly busy this week.

 

Huh, interesting about the fogs & certainly worth noting. Alts are weird, a bad one can behave all sorts of ways. If you can have it tested & confirm that it's bad, replace ASAP. Last time I had what you had was in my Infiniti (and in this particular case it was confirmed 100% to be the alt) I was dead where I parked. Unfortunately they're often not black & white.

 

Can they be tested while on the car at autozone?

 

Crazy, my guess would be alternator as well, but how on earth did you sit there for 15 min with your foot on the brake in drive, that's a crazy long time! Maybe my patience has worn thin while holding the car stationary in drive with my foot on the brake, I usually just put it in park if I know I'm going to be stationary for more than a couple minutes🤷‍♂️

IIRC your car doesn't have a whole lot of miles on it? If it has low miles then it's understandable that you wouldn't have the alternator replaced when the headers were done though. That being said the alternator should be a maintenance item when someone puts headers on the ISF as it's accessible right there. Kind of like replacing the water pump on other vehicles that have a timing belt it just becomes part of the service to save on labor down the road.

 

I'd call around a bit about this. You may even want to check with a dealership - crazy, I know, recommending a dealership - but the right guy & tools would be ideal to properly test an alternator.

 

I did a little testing with my battery tracker. Before it’s warmed up, the battery seems to stay around 13.8-13.9 volts. After it’s warm, it drops to 13.3-13.4. The tester on the app shows a charge consistent with those rates.

What I can’t find is what rate it should charge at. Some posts show 13.9 is the bare minimum, but Lance posted a pic of his charging at 13.3 fully warmed up.

Its possible I slightly taxed the system at the train. All lights were on, including brake lights and fogs, music playing, and I don’t recall if AC was on. After 15 minutes, it’s reasonable to see the voltage dropping. I did hear a small thunk, so that was probably the AC compressor kicking on.

Let me know what charging ranges I’m looking for.

 

Your right, I usually would put it in park. I started my day at 7am, and this was at 10pm at night after doing some presentational stuff. My IQ sharply declines after a 9 hour day. On a long day, I’m surprised I can even figure out how to chew by the time I hit the bed.

 

Hate to pile on about the alternator, but that would be my guess as well. I got 10 years out of the alternator in my 3GS and even with 60k on my 2012 IS-F, I have a feeling i will need to replace it in the next couple years, especially with the added heat with PPE headers without thermal wrap for the past 20k miles.

 

Didn't you just do some wiring repair on your o2 sensors? Could that be related?
And Autozone can test the alternator and battery for free.

 

Correct, I had some poor O2 sensor connections that I repaired about 500 miles ago. It’s been running great. They seem unrelated, but I’m no diagnostic pro. I’ve gotten a lot of feedback on the alternator on Facebook as well lol. As charge gets low on these cars, they behave very oddly, apparently.

 

I've owned my ISF for about 8 years, and this has happened to me a total of 2 times; same setup as OP. I would be in drive (when normally I'd be in Park), and after 10-15mins of being in Drive, I'd hear a loud thud, Parking Brake light would come on, ABS, etc. I'd start driving, and it goes away. I never gave it much thought since it doesn't happen often. fwiw, I have FBO, no wire splicing for O2 sim, battery is about 4 years old, and original alternator.