My battery gauge in the car keeps flickering, if I put a turn signal on the battery gauge move in accordance with the turn signal, If I turn on my lights it puts a drain on my battery as well.

Things I have done

Taken out the aftermarket Stereo
Changed the regulator inside the computer (from several other working computers I have laying around)
Checked my voltages
Changed out the alternator
Brand new battery.

issue still persists.

any help would be great thanks.