i need some input on this please having nothing but problems, has new battery, which has been tested, alternator which has been tested and ecu,,,, will not charge and cant figure out why can charge the battery let it sit a few days it starts right up but battery light comes on shortly after the other dash lights radio shuts off and battery dies out, what do i do

 

have 12volts at the alternator red post wire? have 12volts and a ground pulsing at the other connectors when car running?