Might better start by getting a copy of the wiring diagram for that car. Headlights and brake lights are unswitched,and so should be live with the key off. If hitting the brakes shuts off the car, then you either have a short between the brake light switch and the taillights or when they pull power,it takes away from ignition,which would indicate power supply problems,even something as simple as a bad ground cable can ruin your whole day. Start by checking all connections,and make sure its charging,and when it is it's making it back to the battery. Hope this helps you, Hank