HouseCallAuto 7/5/2013The charging system has to be checked while this light is flashing if at all possible. It is possible that the alternator is junk but just happened to be charging normally when it was checked. You did not say how the car was checked. If you want advice u have to be specific and say details like charging volts. On a Nissan, in almost all or at least any that I remember, a battery and brake light flashing is always a bad alternator but I agree that I have to see the bad alternator with my own eyes before I call it.