i have replaced the battery and the alternator, but my car still dies as soon as i press the brake or use a power window. the headlights dome light and heater still work but if i start it then press brake it dies instantly. also now the airbag light blinks 5 times then 2 times. i dont have a clue whats wrong would the ignition have anything to do with this problem? please help! sometimes when i turn the key to on only the battery light comes on but the heater will work. when i jumped start it all lights come on and it starts but soon as i use the brake or anything it drains and dies!

 

First, check all major wiring connections to be sure they are clean and tight, including the ground wires to the block. Also check to see if the check valve in the brake booster is working properly. It should allow air to flow one way and not the other. The airbag light is intermittent or repaired battery loss feed.