Hello, recently purchased a 2011 Infiniti G37x which just reached 200,000 miles this morning!

Yesterday after having the alternator replaced, it turned on after being jump started and the battery and brake light started flashing and the car seems to be having trouble keeping consistent voltage while driving and sitting at idle. When the car is not running voltage is consistent at 12.9 and 13v. While driving it’s above 13 but when I slow down or come to a stop it’s moving between 12.3 at the lowest and 15.1 I seen as the high, and the battery and brake light comes on and off. Any one had any trouble with this?

 

Battery and brake light flashing means alternator is going bad. Unfortunately, when dealing with aftermarket alternators you risk getting duds. My 1st replacement from Goodyear Auto lasted just 2 months. The replacement for that has been good for a year and a half so far. I knew someone who had a dud fresh out of the box on a new aftermarket one from the parts store. Just gotta replace it until you get one that's not bad.