[Daves55Sedan]

Both the oil and generator idiot lamps have a special isolated lamp socket that is not a standard grounded lamp socket. So if someone has replaced the original sockets with standard sockets, it wont work.
Both sockets have a black/green wire looped to the sockets ending at the ignition switch coil terminal. That is the (-) negative power portion of the circuit. The oil lamp socket has a second wire, white/red that connects to the oil pressure sending unit. That wire runs inside the wire harness and spills out of the harness at the front of the firewall along with the temperature sending unit wire. The white/red band runs down under the exhaust manifold, through the motor mount, then connects to the oil pressure sender with a push-on style terminal. That wire is the (+) positive wire which completes the circuit if the oil pressure is low.