skyline guy

Hi,
UPDATE: Had altenator checked and it is working fine, batteries are fine and charging, but the charge light on dash is staying on. Also cleaned the battery posts and terminals and checked the negative cables all the way down to the engine block. I did recently add power from battery through a circuit breaker to power and electric brake box for camper and power back to the 7 pin connection, but they are both hooked up tight and properly grounded. Any thoughts? Any help or ideas would be greatly appreciated.

1999 F250 super duty / 7.3 ltr. turbo diesel:
Went to start and when I turned the key, everything went dead (lights, dash indicators, everything!). Starter didn't even click. Took off battery cables, and when I put them back on, everything lit up fine. Went to start and same thing happened. Replaced the starter relay on the fender well and seemed to be fine. A few hours later, charge indicator light came on and stayed on. Volt meter on dash stayed steady at 14 or so volts, ran fine, restarted fine, but light stayed on. Took battery cables off again, they are reading 12.5 volts. Hooked them back up, and light is now off. What could be causing this? Altenator???? Followed the negative cables to engine block and they are clean and tight.
Any thoughts?
Thanks for your help!
Greg