Fuel gauge wiring 1940 Hudson

in HUDSON

My basket case came with a restored tank and an new sending unit. I will not be using original wiring harness and will be going 12v after market cheap hot rod wiring kit so will use a voltage reducer for original
gauge. Bottom terminal had one wire top terminal had 3 wires going to it. Is there a simple way to explain how fuel gauge system should be wired?
Comments
BUT OHLMS
I am working on the same problem ... 1940 hudson with 12 volt upgrade ...
Do you know the ohms of the original guage ? Can it be found with a tester ?
Are you stating that 12 volts would work without dropping the voltage to the guage ?
Any help would be appreciated ...
Thanks
New tank and sending unit ... Stainless steel tank
New Sending unit is vdo 226 007 ... 0 ohms empty. 90 ohms full
Assuming the innards of a 40 fuel gauge are the same as those in the the 34 to 39 Mechanical Procedure Manual, on 12V your gauge will theoretically read empty at 300Ω and full at 60Ω. This derives from the fuel gauge test procedure in the manual where it says the gauge should read empty with a current of 0.04A and full with a reading of 0.2A. V=iR and all that.
The gauge is a make and break bimetal strip device as was the sender.