I'm working on a 94 k3500 with a 6.5TD, the volt gauge shows it charging around 12-13 volts (guess) if not a little less. I replaced the alternator and both batteries read around 12.5 volts. I also checked all the battery cables, checking continuity and the wires themselves. I replaced the cable that runs to the starter as well as the wire that runs to the junction block. It'll run for a minute or so and then shut off. The instument cluster will display the battery indicator light and after a minute I'll be able to restart it. Can anyone provide any additional help?