have a 99 ctd and i drove it around the first half of the day and it ran fine. stopped and turned it off ate lunch and went to start it and it made a loud click and that was it. when i turned the key back to off it started clicking and wouldnt stop unilt i unhooked the batteries. Once i turn the key to start i get one turn and the click and thats it. Guy at the auto parts store said check the batteries but the gauge in the truck shows they are charged normal. any ideas on what could cause this??