[Greg Reid]

Originally Posted by "QUICK-SILVER"

Unless the guage IS bad, but then the first empty reading wouldn't have happened.
Unless another possibility, a broken wire in the ribbon running from front to back and wiggiling the harness/connector had it making and breaking contact. But it doesn't really sound like it though.

Think of the fuel guage as an ohm meter, thats only capable of reading 0/zero (dead ground) to 90 ohms. And 0 to 90 is all the sending unit can produce. 0=empty and
90=full.
With the connector unplugged, on the back/trunk side, you can test the sending unit with an ohm meter. Sending unit wire to ground should read 0 to 90 ohms if it's good.

You can perform the same test on the spare sending unit and move the float up and down to see the 0 to 90, if it's good. If it is, hook it to the car harness and see if the fuel guage works.

We're exactly on the same page as far as how it works. I haven't looked at a fuel gauge in a while and don't remember the colors of wires, etc. but it's a very simple, one line series circuit. 12v, gauge, variable resistor {sending unit}, ground.

Keep going Jay. You're close. As Clay said, clip the ohmeter leads to the sending unit and move the lever up and down. You should read a variable resistance from 0 at the bottom to 90 at the top.
OL means it's out of range. I don't know what meter you have but I wouldn't think that 90 ohms would be out of range.