The sending unit in the tank is just a big variable resistor. At full the
gauge gets full current, as the float drops the current runs through
gradually increasing resistance until it reads empty. So, that's why with
the key off the gauge goes to ")"....no juice.

On the back of the gauge check to see if there's any current at the red wire
to the furl gauge. If it does have current, then it's likely not getting a
ground signal through the sender. Run a jumper-wire ground from the pink
wire on the gauge to any good ground. If the gauge goes to full, the sender
or it's wiring is faulty.

 

The sending unit in the tank is just a big variable resistor. At full the
gauge gets full current, as the float drops the current runs through
gradually increasing resistance until it reads empty. So, that's why with
the key off the gauge goes to ")"....no juice.

On the back of the gauge check to see if there's any current at the red wire
to the furl gauge. If it does have current, then it's likely not getting a
ground signal through the sender. Run a jumper-wire ground from the pink
wire on the gauge to any good ground. If the gauge goes to full, the sender
or it's wiring is faulty.