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If the tan wire is connected to the tank resistor then you should read aprox 9 volts with an empty tank.

The 69 fuel gauge resistance between the pink wire (voltage source) and the tan wire is about 44 ohms. The fuel tank resistance with an empty tank is 90 ohms. Total resistance 134 ohms. With 13 volts (a fully charged bat will have about 13 volts) on the pink wire. Using ohms law I= E/R (I is current, E is voltage and R is resistance) so circuit current is 13/134 or 0.097 amps. (97 milliamps) Knowing the circuit current you can determine the voltage drop across the gauge. E = I (0.097) x R (44 gauge resistance) or 4.27 volts. 13 – 4.27 = 8.73 volts would be the voltage drop across the tank resistor. (0.097 x 90) As the tank is filled the tank resistance decreases until with a full tank the resistance is 0 ohms. In this case you will measure 0 volts on the tan wire.
 

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Discussion Starter · #3 ·
Thanks. Right now the wire is just hanging loose by where the gas tank should be I wasnt sure if it was the right wire. My car is a refugee from the dragstrip that I am trying to get back on the street.
 
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