67-72 Chevy Truck fuel gauge diagnostics 101

[Fasteddieb]

Best fuel gauge explanation anywhere. Just got a 69 c10 and it had fuel gauge issues. Turn the key on and the needle went straight to full - and past! Bed mounted fuel cell made things a LOT easier. Took out the sender and it read way over the ohm range. problem is, there was an aftermarket fuel gauge in the dash. Did the PO get the 0 to 90 ohm version? I dunno!
Then I had a brain flash. Went to Radio Shack and purchased a 47 ohm resistor. Hooked it up between the sending wire and ground and turned on the key. Needle went right to 1/2 tank!
Ordered a 0 to 90 ohm sender yesterday. I'll have a working fuel gauge by the weekend!
Thanks guys!
Now I need to work on my wiper motor. It's always something!!!