I have 3 stud fuel gauge on a 1982 olds 88 pulled gauge out and used a test light to check the 3 sockets one on left [looking at the back ] lite up the other 2 did not it is my understanding the one on the right is the ignition 12 volt bottom is ground one on left is sending unit can anyone help me and tell me if I am even close

 

83 but there won't be much difference, if any.