yes, across the gauge will read about 30 ohms, which is why the sender needs to be a 30 ohm one .... that last test was with the gauge out of the dash? if so, was the gauge case grounded to the battery or sender flange?
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics