[Skools Out]

Actually both are right just depends on the gauge you buy. Better ones that have a light in them connect to power and ground at the gauge and they look for a varied ground. but those are one wire sending units

The cheap and dangerous ones have power at the tank. Not the thing i want in my tank is power which can cause corrosion. Especial with a metal tank. Plastic can be dangerous too they will build up static when you have power at the tank.