Almost at the end of a 2000+ mile road trip. While at my last fuel stop, the starter wouldn't engage when I pressed the button. Was too hot and loaded down to bump start it, gave the button one last try and she fired up. Got here and the button again does not work. Battery shows 12.8V. Any clues? I need to get home tomorrow so that I can be ready for a medical procedure on Friday and home is still 500+ miles away.