In my parents car, a 94' jeep grand Cherokee, the electrical wiring is all messed up or something. When I want to listen to the radio, i have to have the headlights on, or else it wont work. If I want to check the vehicle diagnostics on the little screen, the headlights also need to be on! All of the electrical stuff, needs the headlights for them to work! Any ideas on how to fix this, or why its happening?! Thanks