Fuel Gauge Wiring

[SafeAirOne]

The fuel/temp sender circuits are 2 of the simplest circuits on the vehicle. You'll be able to work out your issue or bypass the mess and wire it up correctly to make the system functional without much difficulty.

12v is supplied through a dark green wire (usuallly from a spade connector on the 'downstream' side of the "hot in run" fuse) to either 1) a voltage stabilizer input or 2) directly to the input side of the fuel or temp gauge, then ''piggybacked' on to the input of the other gauge. If a voltage stabilizer is used, then it's the 10v output from the stabilizer that gets 'piggybacked' to the gauge inputs via a light green wire.

The output from the gauges (green with black tracer for the fuel gauge, green with blue tracer for the temp gauge) go to their respective senders, where the resistance is varied based on fuel level or temp, then on to ground to complete the circuit.

[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 a larger wrapped bundle. Having said all that my question is: should there be three wires ( a ground wire?). The fuel gauge seems to work but have no ideas as to accuracy.

[jimrr]

dreddub has this :!, on the wire FROM the tank measure the resistance. also measure the voltage from the vehicle TO the tank. AND OR, you can apply voltage to the wire to the tank with zero or a full tank and measure the resistance. this last tells you if the sender works.

[roverp480]

deleted

[jvsimmons]

Pulled the fuel sensor, turned ignition switch to first position, gounded the sensor to discover after moving the float up and down the shaft that all is good. Low fuel light works as well as the guage. Also think I solved the other electrical issues. Thanks everyone.