diesel fuel gauge quit working

I have a Farm Pro model 2425 tractor and would like to rely on the needle for the fuel gauge. It used to work, and still shows fuel as being in the tank, even when I sucked it dry and got air into the system.  I see a small thin red wire is loose under the panel about where the gauge is, but there is no stripped end or spade type connection on the end of the wire-it's just insulated atll the way to the tip of the wire and I cann't see where it came from.  Any experience with this issue and suggestions to fix will be greatly appreciated.