Car won't start
My wife tried starting 2003 Cadillac CTS last night, heard a loud click, like it came from inside car, headlights came on, clock ran backwards and forwards, door locks cycled thru several times, she turned key off and tried to start again, nothing happened, tried starting it this morning, got a clicking sound from under hood, radio works, A/C works, lights work, clock ran backwards again thern reset to correct time when I pulled key out of ignition, second battery, probably about 5 years old. Could battery be the problem, I heard that you must have some kind of alternate power supplied when changing battery, ios this true?