* From the Fuel Sending Unit: The sending unit wires (typically two: one for ground and one for signal) run from the tank, usually through a hole in the body, protected by grommets or rubber seals. They then follow a route generally along the frame rail or under the floorboard, often bundled with other wiring harnesses.
* Through the Cab: They then proceed into the cab, usually entering through a firewall grommet or penetration near the steering column area.
* To the Instrument Cluster: Finally, they connect to the fuel gauge terminals within the instrument cluster. These terminals are usually on the back of the gauge, making access require removing the instrument cluster.
To trace the wires in your specific truck:
1. Start at the fuel gauge: Remove the instrument cluster bezel and disconnect the fuel gauge. Trace the wires back from their connections.
2. Follow the wires: Be patient and methodical. You may need a wire tracing tool or a test light to follow the path. They'll likely be part of a larger harness.
3. Check the firewall and grommets: Look carefully near the steering column and firewall for wires entering the cab.
4. Follow under the truck (optional): If necessary (and safe to do so), you can look under the truck for the wires running from the tank toward the cab. This will require working on the underside of your truck and may involve some disassembling. Be mindful of any sharp edges or hot components of the exhaust system.
Caution: Working with automotive wiring can be hazardous. Disconnect the battery's negative terminal before starting any wiring work to prevent shorts or accidental shocks. Refer to a 1974 Ford F-100 wiring diagram (available online or in repair manuals) for a more detailed schematic. A factory service manual is the best resource for accurate wiring information.
