When my headlights and anything else is on(radio, rear defrost) my battery light turns on and off really fast(blinks on and off). Does anyone know why it would do that? I checked my battery it fine and i checked how much my alternator is charging and its fine. I'm lost can anyone help?

 

Regulator in the alternator is on its way out. The diodes are fried. Replace your alternator. I know you said you checked it - what was the load test reading on the alternator (what volts at what amps?)?

 

Its reading 13.5volts. I replaced the altenator last year, well i didn't a shop did...do you think they put a weak one in?

 

The static charge volts don't mean ****. You need to see what the alternator is putting out under a load (using a carbon pile to do so).

Alternators go bad. If they installed it and tested it there is nothing more they can do to ensure it is a good unit.