1972 gmc fuel gauge

[Drewbee]

Hey I'm hoping someone can help. First, I know there are a few threads of this topic but they seem scattered in opinions because some people say if it's this it's this, and others say if it's this it's that.

Second, my truck has had some bad wiring from previous owner that I'm trying to correct.

I have replaced everything between the fuel gauge to the sender...even the resistor except the wires. I have gotten the gauge to read at 3 o'clock when the wires is unhooked, and past empty when hooked up.

I checked the new fuel sending unit and was getting 0-90ohms. However because of the previous symptoms described I decided to put the old sending unit in....it now makes a slight clicking sound and bounces around empty. So, I think the new sending unit maybe bad, and the old one is going out that's the reason for the bouncing.

If someone with more knowledge on this please speak in on this. Also, if you say to test the volts or ohms somewhere, pictures would be great and more detail on which lead you put where - such as positive goes here negative goes there.