This is turning out to be more confusing than I expected. The resistance at the gauge between B and T terminals is 60 ohms and T and earth is 100 0hms as you specify and the new sender unit does have a range from 0 – 84 ohms. However the gauge seems to need inputs of between 0 – 190 ohms to register from empty to full, because the new sender at maximum extension shows no more than a quarter full. So something is amiss.
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