No Power 12V.

[STMolo]

Got a weird one but I am sure somebody will have the solution. 2006 3500 MegaCab Cummins 5.9 that started fine three weeks ago and went to leave for work and got 12V but when I turn the key to start. No power and then like the electrical system "reboots" and then try again. Odd thing is I put a jump box on and have steady 12v power but still not enought juice to crank. What could be the issue or drawing power source/problem?

 

[MikeT]

Start simple. Make sure ALL battery connections (both Batteries) are all clean and tight. Remove each terminal one at a time clean both the battery terminal and the cable terminal using a wire brush type terminal cleaner, reinstall and tighten the terminal, then go to the next terminal on the battery. do both batteries. Check individual battery voltage when doing the battery cleaning. Voltage should be over 13 volts if not replace both batteries. (you can temper this last suggestion if the batteries have not been recently charged). After cleaning the batteries up, go to the other ends of the batteries cables, Make sure all connections are clean (clean if not), and again tighten each connection both hot and ground. Many if not most electrical problems can be solved by doing the above.

Mike