Broken fuel guage

Fuel gague has never worked since I have had the car. How do you test that solenoid looking thing in the guage itself? What should I do to test ? 1970 Dodge Challenger

I would disconnect the 2 wires from the gauge & ohm the gauge terminals & see if you have basic continuity. First tho (& way easier) I would pull the blue wire "L" connector off of the tank sender & ground the connector (key on) to a CONFIRMED good ground & see if the gauge needle swings over to the "F" side.

I am guessing you have rally gauges, and the voltage reg is built into the fuel gauge.
If your temp gauge works then it is probably fine.

if it doesn't then you check for pulsing lights on a test light. or a digital volt meter would show 5 volts.

you can test your gauge by wiring 2 AA batteries together in series to get 3 volts and touch the ends to the pos and neg of the gauge to see if it moves.

typically it will be the sending unit, and you can test that as robert spells out above.

Id say 99 % of the timeits the sender.Almost every fuel gauge problem is there.Mostly are bad floats and second is the sender itself.Easy to check.Inhook the wire to sender.Attach a ggod ground to the wire and turn on key if gauge moves its in the sender.Ifnot as said check t see if it pulses to sender.The other big problem is the ground for the sender.many have rusted awy and lots have lost continuity.Oh yeah if your car get a service manual.Rocky

Thanks everyone I will check it out