2019 F350 6.7 diesel, 34,xxx miles. We drove the truck yesterday, made about 10 stops, visiting and shopping. Got home and decided to wash the truck exterior. After washing it got in to move it to the shop, electrical system totally dead. No light, no ding w/key in, door open, no instrument panel lights, no horn and no start. Opened the hood, checked battery voltage, 12.5 +/- on both batteries. Unhooked both batteries for 30-45 sec and reconnected, everything fine, started right up, everything fine today. So just a random gremlin? Called dealer, he said they have heard of it, didn’t seem concerned. If it keeps happening then bring it in. Opinions?

 

You'll always get about the same voltage reading on either battery because they are connected together.

As to the cause of the failure...no idea???

 

Don't know what but something got Wet .. Did You spray the under side of truck ??
Some folks use spray cleaner in the engine compartment then hose it off ??

 

Drivers side battery needs to be checked, its what gives the voltage and inside voltage was probably under 12.5, even 12.4 volts will be a no start. One bad cell in either battery most likely due to age of these batteries, be sure to replace both with same lot/batch.

 

It's time for new batteries, have yours started leaking yet?