So I go out to start up my '94 Pete cabover and as soon as I turn the key to the start position-NOTHING! No low air warning buzzer, no dash lights, no accessories, nothing. It's like the cab has no electrical power at all. The interior light came on for a few seconds and then faded out never to come back on again. I thought it was the batteries so I tried to jump it to no avail. I pulled all four batteries and tested them and they all read fully charged. The battery posts and connections are all clean. So this leads me to believe that a connection is loose or maybe a main fuse is bad. Am I on the right track? This truck has started religiously no matter how cold for as long as I've owned it (about a year and a half) and has been bullet proof reliable until now. Anyone have any ideas? Thanks.

 

check your ground from the batteries to the frame

 

Your ground would be the most suspect, especially if your batteries are charged. I would check all cables starting at the batteries.

 

Yep, what they said.
This is the no.1 place to look.
Lots of vibration loosens even breaks this connection.

 

Yeah, I would check the ground.
If not that, it might be the mother board. The grandmother of them all that runs the whole kit kaboodle. :hellno:

 

Okay I'll check the ground. Thanks for all your suggestions.

 

From your discription, (no accessories) just seems most likely ground strap to the frame. Next suspect for me would be the starter switch, then main fuse.

Is there a battery cutoff switch?

 

Your battery cables may be bad, especially if they are the original ones, some times they corrode from the inside out, ask me how I know :-)