Thanks Gents,
I agree that it's likely grounding. Suspected that the minute I pulled the brake and saw it jump. Looked for frayed wires and found none, so I will continue down that road. Out of curiosity, why would the unit peg all the way to "H" rather than work intermittently at lesser ranges?
I do have the battery neg terminal grounded to the firewall, a ground strap attached between the starter and right toeboard, and a separate 00 cable between the frame and cab.
Bartamos, you mentioned separate ground wires to the gauge cluster rear plate screws. I will try that, but did you have a specific spot that you'd recommend? I did try a test lead ground wire to the chrome part of the cluster before with no results, but I suspect I was not getting an adequate ground.
Also, I had not considered the "idiot light" sender issue. Since N_PA did not have a correct anything for my truck, I got a '66 sender (it matched up in all other respects to what I had), but I don't know how to tell if it's as you describe.
Again, thanks.
Jim
