Re: TR3 Erratic fuel gauge finally quits....testing?
A wire from the battery?
I'd start by using a volt meter to check for 12v on one of the fuel guages terminals, and ground on the other. If you want to see the guage move, dissconnect the side that is not connected to +12v (the sender side) and ground/open it (acting like the sending unit).
You probably have an open to the sending unit, or a bad ground at the sending unit, but it's nothing you can't track down with a cheap multimeter.