Speedo / Tach / Gauges: '56 Golden Hawk gas gauge

[brngarage]

I have a spare '56 Hawk gas gauge and I'd like to test to see if it works. I believe all I need to do is connect 12 volts to the correct terminal and MOMENTARILY ground the other terminal to see the needle move toward the full mark. I have a minor problem before I attempt this; the terminals on the back are not marked (or the markings disappeared over the years). Does someone know whether the upper or lower terminal is the "ignition" terminal? Thanks for the help!

[RadioRoy]

Either terminal will work. It is not polarity sensitive.

Given that, you should not do what you are suggesting. By the time the needle starts to move, you may have already overheated the internals of the gauge. You should measure the resistance of the tank sender and use a resistor around that value in your test.

[brngarage]

Thanks Roy.

[TWChamp]

Roy is right on that. In the 70's I did replace several dash gauges and tank senders. About 90 ohms was the norm for the tank senders, so I just connected my ohm meter to the tank unit and moved the float slowly up and down to make sure the ohms moved evenly between 0 and 90. You could use an old tank unit and battery to test the dash gauge, or just a battery and a 45 ohm resistor rated enough watts to not overheat. At 45 the dash gauge should show about half full. The dash unit works on the heat principal to move, and this way it won't be bouncing around as the gas moves in the tank.