[VetteVet]

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Originally Posted by dave`12

Hello. I have a 67 c10. All the gauges work fine except the fuel gauge. I checked, and the wire from the sending unit has continuity. Also checked the power from the harness (have a wiring diagram) that goes into the cluster that feeds power, it's good. Gauge reads empty.

Pull the tan sending unit wire off at the fuse panel, and turn the key on first. The gauge should go to the 3:00 p'clock position. If it does then put the tan wire back on and then disconnect it at the sending unit on the tank. It should go to the 3:00 o'clock position again, but if it doesn't then the tan wire is grounded between the fuse panel and the sending unit on the tank.

Can anyone tell me how to test the sender? I had it out of the tank when I removed the tank to drain old bad gas. Perhaps I messed it up when I
removed or reinstalled it.

Refer to this thread to test the sender unit and for a complete troublshooting of the gauge and sending unit.

http://67-72chevytrucks.com/vboard/s...d.php?t=640615

Also is it safe to run power directly to the gauge, I'm afraid I might cook it running 12v.

You can put power on the gauge at the no.3 pin on the cluster plug or at the power terminal on the gauge itself but if you have already checked there with the meter you shouldn't have to.
Do not put any power on the tan wire or the Fuel terminal on the fuse panel. Those are the ground sides of the fuel gauge and voltage into the sending unit resistor could heat the resistor on the sending unit to the point that it might ignite the gas fumes in the tank, BOOM, not good.

Or does it run by completing a ground circuit?
Yes, the power goes through the gauge resistor and the gauge coils, then to the tank sending unit resistor,which is a variable resistor that changes resistance to the gauge as the float moves up and down. If you pull the sending unit out of the tank and connect the voltmeter to the terminal and the flange, and move the float arm up and down, it should vary the resistance on the meter between zero and ninety ohms. If the resistance doesn't move off zero then the sending unit is bad.

The printed circuit was replaced when I refurbished the cluster, just about sure it is good.

Any help appreciated.