I have two questions regarding the gauges in my truck.

I have a 55 2nd series and the gas gauge and the temp gauge do not work.

When I pulled the cluster, the temp gauge (which was actually missing) had a real hard thick line (not line a 16 or 18 ga wire), but a solid wire from the sender unit, and was not connected. I replaced the temp gauge and connected based on a wiring diagram that I had found on the internet. It immediately went to HOT when I attached the wires according to the diagram. (I had to wrap a pc of 18 ga wire to the solid pc and taped it together the best I could) The other lead went to the key switch. I reversed the connection to see if it made any difference and it did not work in that position at all. I have not tried it again. So... what is the deal with the big solid wire?
Should I just replace it and the temp sending unit?

On the gas gauge, the tank was rusted out so I replace the tank which came with a built in fuel pump and sender unit as one. I cannot get the gauge to work and I have rewired everything the best that I know how and according to the diagram stated above.

What is the best way to check the gauges to see if they work properly?

Thanks for all the information.

Jeff