Open circuit at fuel sender

[fintubi]

The fuel gauge in ERA 3014 (a slabside with SW gages) has remained off the bottom of the scale, even though I now have 9 gallons onboard.

I disconnected the sender connection behind the wheel well access plate and connected a 210 ohm resistor across the white and black terminals of the chassis harness. This moved the needle up to a reading a little above empty, as expected. I believe this exonerates the wiring at the gage and saves me a foray behind the dash.

When I check the resistance across the corresponding wires (white and black) of the sender harness, I see an open circuit. I'd expect this to be around 100 ohms given the fuel state.

I've heard that grounding of the sender can be an issue due to sealant, but since my car has a dedicated black wire in the sender harness I don't believe I'm reliant on a mechanical ground where the sender mounts to the tank. The black wire in the chassis harness is definitely zero ohms to ground.

Any ideas? I'm mainly interested in knowing whether there's any further debugging I can do with the tank in place. At the moment, this isn't a high enough priority to warrant removing the tank for further investigation.

Bill