Lost all electrical on start

[JakeFromStateFarm]

Hey yall,

2010 Pete 386 with a CM871. Lost all electrical power trying to start. Cleaned starter grounds, tightened battery grounds. Had 5v at mega fuse. Took it off, cleaned it, got power back, 12.7 at mega fuse. Tried to crank...same thing, lost all power, 5v at mega fuse. Repeated process 3 times. Out of water, need help lol.

[Rawze]

bad batteries?.

[tree98]

Load test the batteries. It means absolutely nothing that your volt meter reads 12.7 volts.

[SquareOne]

(07-26-2024 )tree98 Wrote:  Load test the batteries. It means absolutely nothing that your volt meter reads 12.7 volts.

^--- Yep, 100%.....soon as you turn the key that can disappear with a weak set for sure. Check that voltage while trying to crank and report back.

[Btech]

By mega fuse are you talking about the fuse/breaker that's inside the frame by the starter?
If its dropping to 5v there is probably corrosion inside the wire coating going from it to the batteries somewhere. that breaker supplies power to almost everything in the cab.