Hi! I have a 2008 Infiniti G35 and I noticed a while ago that when I reach about 5 or 6K RPMs, a battery and a brake light pop up on my dashboard and disappear momentarily. It's been going on for a few months and I've tried to figure out what it is but to no avail.

Recently the starter also began to have trouble engaging the flywheel and the lights began to flicker whenever the car is running (they don't flicker when the car is off).

I've had a mechanic test my charging system and the alternator and battery both function perfectly and pass all tests. I've checked the grounds and the voltage is all consistent throughout the system. The battery voltage is within the normal range at all times. The engine belt also looks fine.

At one point during acceleration the battery light remained and the car lost all power overnight after I parked it. I got it to the shop and I was already prepared to pay for a new alt but they charged the battery and somehow the car started, the alternator worked once again and passed all the tests. Yet, the car still shows a battery and brake light every time I accelerate.

​​After this, my mechanic basically shrugged and said they'd have to take apart the whole thing to find the issue because they have no clue what it is. I'm kind of stuck and I was wondering if anybody here could at least suggest what could be the issue here? I'm out of guesses for what could be the issue.

 

I had an intermittent alternator in my 2010 Murano that drove me crazy and stranded me before I started watching the battery voltage with a $10 cigarette lighter plug in voltmeter. You can monitor it with an obd scanner/bluetooth dongle setup as well. Basically my alternator output would crap out randomly while driving. And worse, my battery light never even came on. So testing it at one moment in time in your driveway or at the mechanic, it may look good. And then it craps out while you're driving around. The problem is to be SURE it's the alternator and not something else, you need to get it in the not charging state and do the voltage drop tests from battery to B terminal and alternator body to battery negative.

 

Find a new mechanic. If he didn't IMMEDIATELY suspect an intermittently failing alternator then there's some bigger issues with his expertise.

Those are classic signs of an intermittently failing alternator.

 

You'd be surprised how many wacky alternator problems there are in the Murano forum (I know.... different car but lots of similarity under the hood). I don't know why we don't see more here. I'd guess it's the 2nd or 3rd most common failure that I see over there. Even dealer service departments can't figure them out sometimes. One dealer changed a lady's fuel pump and then the car died on the test drive and had to be towed back to the shop. Then they changed the battery and told the lady it was because the tech left the car in acc mode or something. Gave it back to her and it stranded her again in a week. She had the There are so many bad dealer service departments now that have no idea how to debug car problems. Several youtube videos of people taking their Nissans to electrical diagnosis guys after dealers couldn't figure it out. Lotta people think you get the alternator checked and if the machine says it's good, then it's always good.

 

The dealership techs are in many ways handicapped by their service requirements to follow the steps in the FSM. They can only think outside the box to a small degree. Independent technicians however don't have to follow these corporate constraints.

These cars are definitely in that prime age range where alternator failures are a definite thing.