My 76's fuel gauge has never worked. Always assumed it was a sending unit problem, probably a float. Well, drained the tank. took apart the old sending unit and the float was gone! Dropped the tank and found it in several pieces on the bottom. Cool! Replaced the float and put everything back together. Well....fuel gauge still does not work. Ohmed everything, and it looks like it should work until it gets up to the instrument cluster. Kind of at a standstill trying to figure out what direction to go. new gauges? where and how much?
thanks!

tried that this morning and it did nothing...grr

You have to know the OEM low/high resistances and buy a cheap old school volume control or potentiometer that has those values in the spread of the part. Then simply hookup and set potentiometer to low and high values and attach to gauge to make it move.

A potentiometer(used as a volume control on tv's, radios, etc, back in the analog days) is just a variable resistor that you change the resistance of by moving the shaft. What he is saying is to find the high ohm reading and the low ohm reading, (which I think is 0 and 70ish, but I could be wrong) get a pot that covers that range, connect it to the gauge, and move the shaft to see if the gauge needle movement follows as it should.

Of course I am an electronic tech, so what he said makes perfect sense to me. 
I used to have a big box with all that old school stuff in it, but it went away many years and many moves ago. 

Simple, right? 

Russ