I'm having an issue where my brake light and battery light are on at idle but when I Rev, it starts to blink then when i start driving and it's under load, it'll go away. I've changed my alt twice. One with a remanufactured alt and it died on me and the one I have now is not a reman. Just idling I tested it and it's below the voltage needed but I can't really test it while I'm reving it lol. I'm curious if it's just a regulator gone bad, or belt slipping on the ground to the alt came loose because there's not a change in driving whatsoever everything works while I'm driving just fine. Trying to just get to the bottom of it before I'm potentially stranded on the road

 

The FSM has a good troubleshooting guide for charging system issues like this.

https://www.nicoclub.com/infiniti-service-manuals

Typically if you have a battery light at idle but not at 3k rpm, they're going to tell you to inspect your alternator L terminal and S terminal and then belt tension. But it could be anything from loose battery clamps to crappy engine or chassis ground connections on the battery cables. Based on the light being on at idle and not at higher rpm i wouldn't suspect the alternator connector but those get old and brittle and the contacts can get crappy too. So you end up having to check everything to be sure everything's in solid shape. And if you're worried about getting stranded you can buy a little voltmeter that plugs into your cigarette lighter and will display the battery/charging voltage so if your alternator isn't working and you're running off the battery like a total loss system and will get stranded soon, at least you have a heads up so you can go into conservation mode (shut off electrical loads etc.) and make it to someplace safe or maybe back home if it's within a few miles. I went through all this recently.....

You don't say what year/model you have but here's what the FSM looks like for the 2006 G35 sedan.

 

You'll end up doing a voltage drop test as well on the positive and negative side to make sure your battery cable and fusible link to the alternator B terminal is good and the ground connection from the alternator through the engine back to the battery is good. If you have a battery light on at idle you should be able to figure this out because it shouldn't do that so you have the bad condition captured. You just need to make the measurements required to find the source of the problem.

And start with the easy stuff first like make sure your battery is good with 100% certainty. And your battery clamps are clean and tight and don't rotate on the battery terminals.

 

Thanks for the reply and for the info. I'll check those out when I get the chance, and I have a 2003 g35 coupe

 

If it's under 14v at idle it's probably the alternator, but verify the wires are all snug.