hard to say is it a new guage or old ? manufacturer? is it 3 terminal or 2 terminal gauge ? if three will require 1 ignition 12v 2 sender unit connection 3 pernament earth 2 terminal will 1 ignition 2 sender connection . cletis is right above do not use teflon on sender as will negate the earth circuit senders should have a slight taper in the thread and will self seal
new gauges are maked I ignition S sender E earth
hope this helps andrew
