I have an 04 f250 6.0 diesel that when you turn the key on and await the glow plug light to go off the batteries go dead. I have locks, dome light etc. but it won't turn over. The starter may click a bit but that is it. I can put my charger on it for a few minutes and it will start right up. I took it in and had the batteries checked and they are fine. The tech did say at first that there was noise on the circuit, I unplugged the hood light and the noise went away. The next day the same thing, I have had no other problems to speak of and there is 125000 miles on the truck. i just bought the truck last May and have very little knowledge of the workings of a diesel. All help will be very appreciated.

 

Usually when you have to place some kind of additional power to the battery circuit such as a charger to get it to crank/start you have either a high resistance in the battery supply to the vehicle's electrical system or a questionable battery connection.
If the temperature is warm enough the truck will start on one good battery. How did they check the batteries? If one is bad it will pull the good one down.
Were you able to check all the ground and positive side connections right up to the fuse panel?