Feeling pretty stupid today
I dont recall ever having this problem before just bought parts assembled & worked.
But Im doing another, encountered the "key on" gauge pegs situation that Ive now checked with 3 gauges, 2 senders, direct wiring, check & re-check continuity & grounds

Is this failure mode supposed to be TOO MUCH resistance or the LACK OF resistance (open)?

its too MUCH resitance ...
(in my best "chaurch lady" voice) ...nevermind!

@914werke
well mine was doing this when i had a short in the signal on right front and the fuse blew so the gauge was pegged when key was turned on, is this what you are talking about being "too much" , it was a short in my situation , i have to replace the right front signal socket , i thought it was either the fog light switch, flasher or signal relay , and that was why i had asked you about the fog light switch. . if so where was your short?

I deleted some bad info I posted.
I just read that if it pegs with key on and engine off the wire to sender is open.
I wonder if you put a ground directly to the gauge and it doesn't peg that verifies an open wire since you had already replaced the sender.

So what was the fix.. I am experiencing something similar right now as well with oil pressure and fuel gauge..