I have a 2009 nissan titan a couple days ago the battery an brake light started flashing, so I changed the alternator and I'm not getting any charge going to battery. new alternator has passed test and battery has passed test, when I check voltage on battery is 12.4 not running and 12.9 running any ideas what it could be? iv spent 3 days going through stuff an I cannot find a problem any help is very well appreciated!