My son was driving my 2002 Deville, he just got off the interstate 140 mile trip. Car dash alarm went off, car died and will not restart. Headlight would not turn off even with key pulled and doors locked. Checked the battery was low due to setting with headlights on for a couple hours. battery was fine. I have power to all gauges and headlights still remain on after installing battery. Can not get power to starter. Relay clicks when the key is turned. Any helpful ideas?