Sounds like it could be one of the fusible links making intermittent contact.
Driver's fender under the hood coil spring INSIDE the wire loom....
They look like regular wires except the have a short piece of what looks llike heat shrink tubing. inside the 'heat shrink' is the link.
Instead of fuses that can be replaced - the wire actually burns apart. I believe it's the white one that controls the ASD - which controls the A/C, Alt, and Cruise...
That's what my problem was when it went haywire.....
Hope it's yours also.

 

When I was shopping for my truck I looked at this 93 w250 cummins auto. with the wire harrness ripped apart and retaped with new tape and asked whasup with this and he said had a problem and it was the fuseable link they finally found but don't remember what the prob was. Sounds alike. Dave

 

what seats are those? the seat itself looks like my 92 but the fabric is different for sure. looks like a mini van or neon material

 

They look just like a friend of mines in his 99 cummins.I think there 2nd gens?

 

Those are 1st gen 'Captains chairs.' 2nd gen's don't have the armrest. That fabric is 2nd gen vintage though, same as my 98.5. Sweet truck BTW rockmike, very nice!