Missed yer post; this may sound strange, but I often have other things to do besides work on or diagnose my car issues online, and the Brickboard is a proven time vortex, capable of making whole days vanish into thin air if I start reading posts...&^)

I posted about this some months ago, you could search for that one, and got some answers, mostly saying that the senders don't often go bad, but the wiring does.

So I messed with the wiring at both ends, to no good end.

I'd try another speedo, but since the whole thing works/quits I keep thinking that the speedo/odo is good, and there's another problem, whatever it might be.

Replacing that rear section of wire is a PITA, the test lead won't go through the stock sleeve, so used long lengths of duct tape wrapped longitudinally on the wires from opposite sides, and then threaded that mess through.

Used dilectric grease on the plug as well, but will go back in and tighten the plug connections when I can get under the car again.

Meanwhile wondering if it's worth continuing to chase electrical gremlins on the old girl, or if I should just have her parted and crushed in the name of sanity (mine).