Nope. It was not the cluster--
15 ohms at the sender plug, even when full
I was at the Junkyard today and saw a fuel sender laying on top of a fuel tank inside a 1st gen
I brought it home, and found what causes them to fail.
The sender will come apart, and, inside is a 2 fingered prong contact which rotates against the metal backing plate. This is the ground path for the sender.
Probing it with a meter showed it was opened, in all positions.
I took it all apart and sandblasted the backing plate. ( sandpaper would work also)
I then re assembled it and sprayed electronics parts cleaner inside, blew it out with air and sprayed it down again, right through the cleaning hole which is provided in the plastic housing
now I have a smooth operating sender.
It rises up the resistance scale with no flickers from my meter.
I heated the float with a propane torch, brushed on some flux and soldered the tiny holes closed. There is a product called "seal all" which I will coat it with also just to be sure.
You may call me cheap, but I have a total of about 25 minutes into a good working sender. I am broke, and I recycled a part. Hopefully.