Veeeeerry interesting! I did some snooping, and I think that wire from the sending unit that goes to the fuse block [not powered, just a connection point] continues on through a harness to the ground side of the fuel gauge.
Could the gauge clusters in these trucks be plastic, or mounted in plastic.
I don't have a wiring diagram, or a book, so I might be all wet, but this is how it appears to work.
The connection in the fuse block is not a "hot" connection...just a connection for a secure ground to the gauge.
Stuart
