1983 Series 3 diesel fuel sender wiring

[jvsimmons]

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

[roverp480]

According to the workshop manual the sender has just two "Lucar" connections . One as you say marked W to the warning light and the other marked T to gauge . The body is earthed through the tank sender unit fixings to the frame to make the final electrical connection . Some later sender units have a third Lucar which can be used to make a earth connection via a wire . This one can be identified as it is welded to the body of the sender unit whereas the other two are insulated, passing through the body to the connections inside. It may be worth connecting a black wire (to conform with the British color coding ) from the earth Lucar to the body or frame to improve the circuit. Your warning light should illuminate if you disconnect the W wire at the sender and touch it to the sender body. Presumably you have checked the bulb. You may have these but extracts from LR workshop Manual. 139171391813919

[jvsimmons]

Thank you for the help. Indeed connecting the "W" wire to ground caused the low fuel light to come on. I really should pull the sender unit from the tank and test to see if I can get the low fuel light to come on. I do have the manual from which you forwarded to diagrams - the manual is good for telling one how to remove and install something but weak on diagnostics. All this started when my brake switch shorted and blew one of the 35 amp fuses. While trying to diagnose why the fuse was blown I pulled the instrument panel out and a few wires became disconnected ( finally found the bad brake switch and replaced it). Then I could not figure out where the disconnected wires went - then did something stupid and made my electrical problem worse. Had to replace the turn signal/horn button/headlight dimmer switch and the panel light switch. I have figured out what wires go where but one light function does not work ( fender side lights). Found the terminal on a multiplug behind the instrument panel that feeds power to the side lights by using a hot lead but cannot figure out why that line doesn't get power when the headlight switch is flipped to either the center or lower position. The wiring diagram in the manual shows that it should come off of terminal 7 of the main light switch with a red wire. There is no red wire to be found. My model is the County with driving lights attached to the front bumper and there is a relay to feeds power to these light, so maybe the wiring configuration in my truck is not exactly like found in the workshop manual. Thoughts?