I have an 1983 S3 diesel 88 station wagon. I have been attempting to diagnose why my low fuel warning light does not work. I have read many post about the fuel sending unit. I have discovered in my readings that one of the bayonet connectors on top of the sender is marked with a "W" to indicate where the wire for the low fuel light is connected. I assume then that one of the other two remaining connectors is for the fuel gauge. My S3 only has two wires connected to the sender. I am still trying to trace these wires once they enter the bulkhead - having some difficulty because the previous owner installed a new harness but some of the wires ( like the ones connected to the fuel sender) are not the correct color as shown in wiring diagrams. And behind the instrument panel is a plate of spaghetti with wires disappearing in larger wrapped bundles. Having said all that my question is: should there be three wires connected to the fuel sender ( a ground wire?). The fuel gauge seems to work but have no idea as to accuracy. Thanks for any help. Jim