Bad Fuel Gauge?

[gringoloco]

Starting form the top:

- The factory fuel gauge was pegged when I bought the truck (disconnected).

- Aftermarket oversize fuel tank. There was an aftermarket sender/gauge setup, that was inaccurate.

- I replaced the sender with a 0-90 ohm unit so I could use the factory gauge with the aftermarket tank. Tested sender before install w/ DMM 0 empty, 90 full, and smooth transition between.

- Double checked the readings post install, still good

- Re-installed tank, w/ new sender, wired an extra ground to be sure, trashed aftermarket gauge, reconnected brown wire to fuse box and went for a fill-up

-Filled tank about half full, but gauge reads less than 1/8th?

- Pulled brown wire at cluster, ohmmeter shows 42 ohms between wire and ground, which I figure should read just under half on the gauge.

Bad gauge? Never had one fail on me, so I'm not sure if this is how it would manifest...

Thanks for the help/ideas